420 lines
13 KiB
LLVM
420 lines
13 KiB
LLVM
; RUN: opt < %s -analyze -block-freq | FileCheck %s
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; RUN: opt < %s -passes='print<block-freq>' -disable-output 2>&1 | FileCheck %s
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; A loop with multiple exits isn't irreducible. It should be handled
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; correctly.
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;
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; CHECK-LABEL: Printing analysis {{.*}} for function 'multiexit':
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; CHECK-NEXT: block-frequency-info: multiexit
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define void @multiexit(i1 %x) {
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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entry:
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br label %loop.1
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; CHECK-NEXT: loop.1: float = 2.0,
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loop.1:
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br i1 %x, label %exit.1, label %loop.2, !prof !0
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; CHECK-NEXT: loop.2: float = 1.75,
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loop.2:
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br i1 %x, label %exit.2, label %loop.1, !prof !1
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; CHECK-NEXT: exit.1: float = 0.25,
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exit.1:
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br label %return
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; CHECK-NEXT: exit.2: float = 0.75,
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exit.2:
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br label %return
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; CHECK-NEXT: return: float = 1.0, int = [[ENTRY]]
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return:
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ret void
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}
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!0 = !{!"branch_weights", i32 1, i32 7}
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!1 = !{!"branch_weights", i32 3, i32 4}
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; Irreducible control flow
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; ========================
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;
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; LoopInfo defines a loop as a non-trivial SCC dominated by a single block,
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; called the header. A given loop, L, can have sub-loops, which are loops
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; within the subgraph of L that excludes the header.
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;
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; In addition to loops, -block-freq has limited support for irreducible SCCs,
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; which are SCCs with multiple entry blocks. Irreducible SCCs are discovered
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; on they fly, and modelled as loops with multiple headers.
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;
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; The headers of irreducible sub-SCCs consist of its entry blocks and all nodes
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; that are targets of a backedge within it (excluding backedges within true
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; sub-loops).
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;
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; -block-freq is currently designed to act like a block is inserted that
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; intercepts all the edges to the headers. All backedges and entries point to
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; this block. Its successors are the headers, which split the frequency
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; evenly.
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;
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; There are a number of testcases below. Only the first two have detailed
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; explanations.
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;
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; Testcase #1
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; ===========
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;
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; In this case c1 and c2 should have frequencies of 15/7 and 13/7,
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; respectively. To calculate this, consider assigning 1.0 to entry, and
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; distributing frequency iteratively (to infinity). At the first iteration,
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; entry gives 3/4 to c1 and 1/4 to c2. At every step after, c1 and c2 give 3/4
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; of what they have to each other. Somehow, all of it comes out to exit.
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;
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; c1 = 3/4 + 1/4*3/4 + 3/4*3^2/4^2 + 1/4*3^3/4^3 + 3/4*3^3/4^3 + ...
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; c2 = 1/4 + 3/4*3/4 + 1/4*3^2/4^2 + 3/4*3^3/4^3 + 1/4*3^3/4^3 + ...
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;
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; Simplify by splitting up the odd and even terms of the series and taking out
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; factors so that the infite series matches:
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;
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; c1 = 3/4 *(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
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; + 3/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
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; c2 = 1/4 *(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
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; + 9/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
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;
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; c1 = 15/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
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; c2 = 13/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
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;
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; Since this geometric series sums to 16/7:
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;
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; c1 = 15/7
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; c2 = 13/7
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;
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; If we treat c1 and c2 as members of the same loop, the exit frequency of the
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; loop as a whole is 1/4, so the loop scale should be 4. Summing c1 and c2
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; gives 28/7, or 4.0, which is nice confirmation of the math above.
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;
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; -block-freq currently treats the two nodes as equals.
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define void @multientry(i1 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'multientry':
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; CHECK-NEXT: block-frequency-info: multientry
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br i1 %x, label %c1, label %c2, !prof !2
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c1:
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; CHECK-NEXT: c1: float = 2.0,
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; The "correct" answer is: float = 2.142857{{[0-9]*}},
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br i1 %x, label %c2, label %exit, !prof !2
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c2:
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; CHECK-NEXT: c2: float = 2.0,
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; The "correct" answer is: float = 1.857142{{[0-9]*}},
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br i1 %x, label %c1, label %exit, !prof !2
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!2 = !{!"branch_weights", i32 3, i32 1}
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; Testcase #2
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; ===========
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;
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; In this case c1 and c2 should be treated as equals in a single loop. The
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; exit frequency is 1/3, so the scaling factor for the loop should be 3.0. The
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; loop is entered 2/3 of the time, and c1 and c2 split the total loop frequency
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; evenly (1/2), so they should each have frequencies of 1.0 (3.0*2/3*1/2).
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; Another way of computing this result is by assigning 1.0 to entry and showing
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; that c1 and c2 should accumulate frequencies of:
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;
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; 1/3 + 2/9 + 4/27 + 8/81 + ...
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; 2^0/3^1 + 2^1/3^2 + 2^2/3^3 + 2^3/3^4 + ...
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;
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; At the first step, c1 and c2 each get 1/3 of the entry. At each subsequent
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; step, c1 and c2 each get 1/3 of what's left in c1 and c2 combined. This
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; infinite series sums to 1.
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define void @crossloops(i2 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'crossloops':
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; CHECK-NEXT: block-frequency-info: crossloops
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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switch i2 %x, label %exit [ i2 1, label %c1
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i2 2, label %c2 ], !prof !3
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c1:
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; CHECK-NEXT: c1: float = 1.0,
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switch i2 %x, label %exit [ i2 1, label %c1
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i2 2, label %c2 ], !prof !3
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c2:
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; CHECK-NEXT: c2: float = 1.0,
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switch i2 %x, label %exit [ i2 1, label %c1
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i2 2, label %c2 ], !prof !3
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!3 = !{!"branch_weights", i32 2, i32 2, i32 2}
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; A true loop with irreducible control flow inside.
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define void @loop_around_irreducible(i1 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_irreducible':
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; CHECK-NEXT: block-frequency-info: loop_around_irreducible
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br label %loop
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loop:
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; CHECK-NEXT: loop: float = 4.0, int = [[HEAD:[0-9]+]]
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br i1 %x, label %left, label %right, !prof !4
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left:
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; CHECK-NEXT: left: float = 8.0,
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br i1 %x, label %right, label %loop.end, !prof !5
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right:
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; CHECK-NEXT: right: float = 8.0,
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br i1 %x, label %left, label %loop.end, !prof !5
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loop.end:
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; CHECK-NEXT: loop.end: float = 4.0, int = [[HEAD]]
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br i1 %x, label %loop, label %exit, !prof !5
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!4 = !{!"branch_weights", i32 1, i32 1}
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!5 = !{!"branch_weights", i32 3, i32 1}
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; Two unrelated irreducible SCCs.
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define void @two_sccs(i1 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'two_sccs':
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; CHECK-NEXT: block-frequency-info: two_sccs
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br i1 %x, label %a, label %b, !prof !6
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a:
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; CHECK-NEXT: a: float = 0.75,
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br i1 %x, label %a.left, label %a.right, !prof !7
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a.left:
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; CHECK-NEXT: a.left: float = 1.5,
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br i1 %x, label %a.right, label %exit, !prof !6
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a.right:
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; CHECK-NEXT: a.right: float = 1.5,
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br i1 %x, label %a.left, label %exit, !prof !6
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b:
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; CHECK-NEXT: b: float = 0.25,
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br i1 %x, label %b.left, label %b.right, !prof !7
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b.left:
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; CHECK-NEXT: b.left: float = 0.625,
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br i1 %x, label %b.right, label %exit, !prof !8
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b.right:
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; CHECK-NEXT: b.right: float = 0.625,
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br i1 %x, label %b.left, label %exit, !prof !8
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!6 = !{!"branch_weights", i32 3, i32 1}
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!7 = !{!"branch_weights", i32 1, i32 1}
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!8 = !{!"branch_weights", i32 4, i32 1}
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; A true loop inside irreducible control flow.
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define void @loop_inside_irreducible(i1 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_inside_irreducible':
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; CHECK-NEXT: block-frequency-info: loop_inside_irreducible
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br i1 %x, label %left, label %right, !prof !9
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left:
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; CHECK-NEXT: left: float = 2.0,
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br i1 %x, label %right, label %exit, !prof !10
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right:
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; CHECK-NEXT: right: float = 2.0, int = [[RIGHT:[0-9]+]]
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br label %loop
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loop:
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; CHECK-NEXT: loop: float = 6.0,
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br i1 %x, label %loop, label %right.end, !prof !11
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right.end:
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; CHECK-NEXT: right.end: float = 2.0, int = [[RIGHT]]
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br i1 %x, label %left, label %exit, !prof !10
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!9 = !{!"branch_weights", i32 1, i32 1}
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!10 = !{!"branch_weights", i32 3, i32 1}
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!11 = !{!"branch_weights", i32 2, i32 1}
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; Irreducible control flow in a branch that's in a true loop.
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define void @loop_around_branch_with_irreducible(i1 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_branch_with_irreducible':
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; CHECK-NEXT: block-frequency-info: loop_around_branch_with_irreducible
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br label %loop
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loop:
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; CHECK-NEXT: loop: float = 2.0, int = [[LOOP:[0-9]+]]
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br i1 %x, label %normal, label %irreducible.entry, !prof !12
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normal:
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; CHECK-NEXT: normal: float = 1.5,
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br label %loop.end
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irreducible.entry:
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; CHECK-NEXT: irreducible.entry: float = 0.5, int = [[IRREDUCIBLE:[0-9]+]]
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br i1 %x, label %left, label %right, !prof !13
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left:
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; CHECK-NEXT: left: float = 1.0,
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br i1 %x, label %right, label %irreducible.exit, !prof !12
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right:
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; CHECK-NEXT: right: float = 1.0,
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br i1 %x, label %left, label %irreducible.exit, !prof !12
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irreducible.exit:
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; CHECK-NEXT: irreducible.exit: float = 0.5, int = [[IRREDUCIBLE]]
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br label %loop.end
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loop.end:
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; CHECK-NEXT: loop.end: float = 2.0, int = [[LOOP]]
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br i1 %x, label %loop, label %exit, !prof !13
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!12 = !{!"branch_weights", i32 3, i32 1}
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!13 = !{!"branch_weights", i32 1, i32 1}
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; Irreducible control flow between two true loops.
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define void @loop_around_branch_with_irreducible_around_loop(i1 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_branch_with_irreducible_around_loop':
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; CHECK-NEXT: block-frequency-info: loop_around_branch_with_irreducible_around_loop
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br label %loop
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loop:
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; CHECK-NEXT: loop: float = 3.0, int = [[LOOP:[0-9]+]]
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br i1 %x, label %normal, label %irreducible, !prof !14
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normal:
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; CHECK-NEXT: normal: float = 2.0,
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br label %loop.end
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irreducible:
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; CHECK-NEXT: irreducible: float = 1.0,
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br i1 %x, label %left, label %right, !prof !15
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left:
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; CHECK-NEXT: left: float = 2.0,
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br i1 %x, label %right, label %loop.end, !prof !16
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right:
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; CHECK-NEXT: right: float = 2.0, int = [[RIGHT:[0-9]+]]
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br label %right.loop
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right.loop:
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; CHECK-NEXT: right.loop: float = 10.0,
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br i1 %x, label %right.loop, label %right.end, !prof !17
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right.end:
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; CHECK-NEXT: right.end: float = 2.0, int = [[RIGHT]]
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br i1 %x, label %left, label %loop.end, !prof !16
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loop.end:
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; CHECK-NEXT: loop.end: float = 3.0, int = [[LOOP]]
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br i1 %x, label %loop, label %exit, !prof !14
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!14 = !{!"branch_weights", i32 2, i32 1}
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!15 = !{!"branch_weights", i32 1, i32 1}
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!16 = !{!"branch_weights", i32 3, i32 1}
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!17 = !{!"branch_weights", i32 4, i32 1}
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; An irreducible SCC with a non-header.
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define void @nonheader(i1 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'nonheader':
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; CHECK-NEXT: block-frequency-info: nonheader
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br i1 %x, label %left, label %right, !prof !18
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left:
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; CHECK-NEXT: left: float = 1.0,
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br i1 %x, label %bottom, label %exit, !prof !19
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right:
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; CHECK-NEXT: right: float = 1.0,
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br i1 %x, label %bottom, label %exit, !prof !20
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bottom:
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; CHECK-NEXT: bottom: float = 1.0,
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br i1 %x, label %left, label %right, !prof !18
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!18 = !{!"branch_weights", i32 1, i32 1}
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!19 = !{!"branch_weights", i32 1, i32 3}
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!20 = !{!"branch_weights", i32 3, i32 1}
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; An irreducible SCC with an irreducible sub-SCC. In the current version of
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; -block-freq, this means an extra header.
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;
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; This testcases uses non-trivial branch weights. The CHECK statements here
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; will start to fail if we change -block-freq to be more accurate. Currently,
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; loop headers are affected by the weight of their corresponding back edges.
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define void @nonentry_header(i1 %x, i2 %y) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'nonentry_header':
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; CHECK-NEXT: block-frequency-info: nonentry_header
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br i1 %x, label %left, label %right, !prof !21
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left:
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; CHECK-NEXT: left: float = 0.14
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br i1 %x, label %top, label %bottom, !prof !22
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right:
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; CHECK-NEXT: right: float = 0.42
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br i1 %x, label %top, label %bottom, !prof !22
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top:
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; CHECK-NEXT: top: float = 8.43
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switch i2 %y, label %exit [ i2 0, label %left
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i2 1, label %right
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i2 2, label %bottom ], !prof !23
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bottom:
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; CHECK-NEXT: bottom: float = 4.5,
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br label %top
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!21 = !{!"branch_weights", i32 2, i32 1}
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!22 = !{!"branch_weights", i32 1, i32 1}
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!23 = !{!"branch_weights", i32 8, i32 1, i32 3, i32 12}
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