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3bb84c9bcc
The C and C++ semantics for compare_exchange require it to return a bool
indicating success. This gets mapped to LLVM IR which follows each cmpxchg with
an icmp of the value loaded against the desired value.
When lowered to ldxr/stxr loops, this extra comparison is redundant: its
results are implicit in the control-flow of the function.
This commit makes two changes: it replaces that icmp with appropriate PHI
nodes, and then makes sure earlyCSE is called after expansion to actually make
use of the opportunities revealed.
I've also added -{arm,aarch64}-enable-atomic-tidy options, so that
existing fragile tests aren't perturbed too much by the change. Many
of them either rely on undef/unreachable too pervasively to be
restored to something well-defined (particularly while making sure
they test the same obscure assert from many years ago), or depend on a
particular CFG shape, which is disrupted by SimplifyCFG.
rdar://problem/16227836
llvm-svn: 209883
30 lines
749 B
LLVM
30 lines
749 B
LLVM
; RUN: llc < %s -mtriple=thumbv7-none-linux-gnueabi -arm-atomic-cfg-tidy=0 | FileCheck %s
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; PR4659
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; PR4682
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define hidden i32 @__gcov_execlp(i8* %path, i8* %arg, ...) nounwind {
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entry:
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; CHECK-LABEL: __gcov_execlp:
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; CHECK: sub sp, #8
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; CHECK: push
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; CHECK: add r7, sp, #4
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; CHECK: sub.w r4, r7, #4
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; CHECK: mov sp, r4
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; CHECK-NOT: mov sp, r7
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; CHECK: add sp, #8
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call void @__gcov_flush() nounwind
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br i1 undef, label %bb5, label %bb
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bb: ; preds = %bb, %entry
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br i1 undef, label %bb5, label %bb
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bb5: ; preds = %bb, %entry
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%0 = alloca i8*, i32 undef, align 4 ; <i8**> [#uses=1]
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%1 = call i32 @execvp(i8* %path, i8** %0) nounwind ; <i32> [#uses=1]
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ret i32 %1
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}
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declare hidden void @__gcov_flush()
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declare i32 @execvp(i8*, i8**) nounwind
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