155 lines
3.3 KiB
LLVM
155 lines
3.3 KiB
LLVM
; bswap should be constant folded when it is passed a constant argument
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; RUN: llc < %s -march=x86 -mcpu=i686 | FileCheck %s
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; RUN: llc < %s -march=x86-64 | FileCheck %s --check-prefix=CHECK64
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declare i16 @llvm.bswap.i16(i16)
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declare i32 @llvm.bswap.i32(i32)
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declare i64 @llvm.bswap.i64(i64)
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define i16 @W(i16 %A) {
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; CHECK-LABEL: W:
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; CHECK: rolw $8, %ax
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; CHECK64-LABEL: W:
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; CHECK64: rolw $8, %
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%Z = call i16 @llvm.bswap.i16( i16 %A ) ; <i16> [#uses=1]
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ret i16 %Z
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}
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define i32 @X(i32 %A) {
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; CHECK-LABEL: X:
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; CHECK: bswapl %eax
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; CHECK64-LABEL: X:
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; CHECK64: bswapl %
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%Z = call i32 @llvm.bswap.i32( i32 %A ) ; <i32> [#uses=1]
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ret i32 %Z
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}
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define i64 @Y(i64 %A) {
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; CHECK-LABEL: Y:
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; CHECK: bswapl %eax
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; CHECK: bswapl %edx
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; CHECK64-LABEL: Y:
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; CHECK64: bswapq %
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%Z = call i64 @llvm.bswap.i64( i64 %A ) ; <i64> [#uses=1]
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ret i64 %Z
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}
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; rdar://9164521
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define i32 @test1(i32 %a) nounwind readnone {
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entry:
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; CHECK-LABEL: test1:
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; CHECK: bswapl [[REG:%.*]]
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; CHECK: shrl $16, [[REG]]
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; CHECK64-LABEL: test1:
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; CHECK64: bswapl [[REG:%.*]]
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; CHECK64: shrl $16, [[REG]]
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%and = lshr i32 %a, 8
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%shr3 = and i32 %and, 255
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%and2 = shl i32 %a, 8
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%shl = and i32 %and2, 65280
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%or = or i32 %shr3, %shl
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ret i32 %or
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}
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define i32 @test2(i32 %a) nounwind readnone {
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entry:
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; CHECK-LABEL: test2:
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; CHECK: bswapl [[REG:%.*]]
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; CHECK: sarl $16, [[REG]]
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; CHECK64-LABEL: test2:
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; CHECK64: bswapl [[REG:%.*]]
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; CHECK64: sarl $16, [[REG]]
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%and = lshr i32 %a, 8
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%shr4 = and i32 %and, 255
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%and2 = shl i32 %a, 8
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%or = or i32 %shr4, %and2
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%sext = shl i32 %or, 16
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%conv3 = ashr exact i32 %sext, 16
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ret i32 %conv3
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}
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@var8 = global i8 0
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@var16 = global i16 0
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; The "shl" below can move bits into the high parts of the value, so the
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; operation is not a "bswap, shr" pair.
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; rdar://problem/14814049
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define i64 @not_bswap() {
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; CHECK-LABEL: not_bswap:
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; CHECK-NOT: bswapl
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; CHECK: ret
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; CHECK64-LABEL: not_bswap:
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; CHECK64-NOT: bswapq
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; CHECK64: ret
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%init = load i16, i16* @var16
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%big = zext i16 %init to i64
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%hishifted = lshr i64 %big, 8
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%loshifted = shl i64 %big, 8
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%notswapped = or i64 %hishifted, %loshifted
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ret i64 %notswapped
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}
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; This time, the lshr (and subsequent or) is completely useless. While it's
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; technically correct to convert this into a "bswap, shr", it's suboptimal. A
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; simple shl works better.
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define i64 @not_useful_bswap() {
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; CHECK-LABEL: not_useful_bswap:
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; CHECK-NOT: bswapl
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; CHECK: ret
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; CHECK64-LABEL: not_useful_bswap:
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; CHECK64-NOT: bswapq
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; CHECK64: ret
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%init = load i8, i8* @var8
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%big = zext i8 %init to i64
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%hishifted = lshr i64 %big, 8
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%loshifted = shl i64 %big, 8
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%notswapped = or i64 %hishifted, %loshifted
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ret i64 %notswapped
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}
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; Finally, it *is* OK to just mask off the shl if we know that the value is zero
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; beyond 16 bits anyway. This is a legitimate bswap.
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define i64 @finally_useful_bswap() {
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; CHECK-LABEL: finally_useful_bswap:
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; CHECK: bswapl [[REG:%.*]]
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; CHECK: shrl $16, [[REG]]
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; CHECK: ret
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; CHECK64-LABEL: finally_useful_bswap:
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; CHECK64: bswapq [[REG:%.*]]
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; CHECK64: shrq $48, [[REG]]
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; CHECK64: ret
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%init = load i16, i16* @var16
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%big = zext i16 %init to i64
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%hishifted = lshr i64 %big, 8
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%lomasked = and i64 %big, 255
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%loshifted = shl i64 %lomasked, 8
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%swapped = or i64 %hishifted, %loshifted
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ret i64 %swapped
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}
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