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08762f9f1e
An identity COPY like this: %AL = COPY %AL, %EAX<imp-def> has no semantic effect, but encodes liveness information: Further users of %EAX only depend on this instruction even though it does not define the full register. Replace the COPY with a KILL instruction in those cases to maintain this liveness information. (This reverts a small part of r238588 but this time adds a comment explaining why a KILL instruction is useful). llvm-svn: 274952
56 lines
1.5 KiB
LLVM
56 lines
1.5 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
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; RUN: llc < %s -mtriple=i686-unknown | FileCheck %s --check-prefix=X32
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; RUN: llc < %s -mtriple=x86_64-unknown | FileCheck %s --check-prefix=X64
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; Use movzbl to avoid partial-register updates.
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define i32 @foo(i32 %p, i8 zeroext %x) nounwind {
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; X32-LABEL: foo:
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; X32: # BB#0:
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; X32-NEXT: movzbl {{[0-9]+}}(%esp), %eax
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; X32-NEXT: # kill: %EAX<def> %EAX<kill> %AX<def>
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; X32-NEXT: divb {{[0-9]+}}(%esp)
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; X32-NEXT: movzbl %al, %eax
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; X32-NEXT: andl $1, %eax
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; X32-NEXT: retl
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;
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; X64-LABEL: foo:
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; X64: # BB#0:
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; X64-NEXT: movzbl %dil, %eax
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; X64-NEXT: # kill: %EAX<def> %EAX<kill> %AX<def>
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; X64-NEXT: divb %sil
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; X64-NEXT: movzbl %al, %eax
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; X64-NEXT: andl $1, %eax
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; X64-NEXT: retq
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%q = trunc i32 %p to i8
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%r = udiv i8 %q, %x
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%s = zext i8 %r to i32
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%t = and i32 %s, 1
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ret i32 %t
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}
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define i32 @bar(i32 %p, i16 zeroext %x) nounwind {
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; X32-LABEL: bar:
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; X32: # BB#0:
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; X32-NEXT: movzwl {{[0-9]+}}(%esp), %eax
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; X32-NEXT: xorl %edx, %edx
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; X32-NEXT: divw {{[0-9]+}}(%esp)
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; X32-NEXT: # kill: %AX<def> %AX<kill> %EAX<def>
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; X32-NEXT: andl $1, %eax
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; X32-NEXT: retl
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;
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; X64-LABEL: bar:
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; X64: # BB#0:
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; X64-NEXT: xorl %edx, %edx
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; X64-NEXT: movl %edi, %eax
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; X64-NEXT: divw %si
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; X64-NEXT: # kill: %AX<def> %AX<kill> %EAX<def>
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; X64-NEXT: andl $1, %eax
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; X64-NEXT: retq
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%q = trunc i32 %p to i16
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%r = udiv i16 %q, %x
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%s = zext i16 %r to i32
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%t = and i32 %s, 1
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ret i32 %t
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}
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