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Add comments and test for atomic load/store and mem2reg. 

llvm-svn: 137690
This commit is contained in:
Eli Friedman 2011-08-15 23:55:52 +00:00
parent 07bb9eea33
commit 01a67111d1
2 changed files with 16 additions and 0 deletions
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4
llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
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@ -86,11 +86,15 @@ bool llvm::isAllocaPromotable(const AllocaInst *AI) {
UI != UE; ++UI) { // Loop over all of the uses of the alloca
const User *U = *UI;
if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
// Note that atomic loads can be transformed; atomic semantics do
// not have any meaning for a local alloca.
if (LI->isVolatile())
return false;
} else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
if (SI->getOperand(0) == AI)
return false; // Don't allow a store OF the AI, only INTO the AI.
// Note that atomic stores can be transformed; atomic semantics do
// not have any meaning for a local alloca.
if (SI->isVolatile())
return false;
} else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) {

12
llvm/test/Transforms/Mem2Reg/atomic.ll Normal file
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@ -0,0 +1,12 @@
; RUN: opt -mem2reg < %s -S | FileCheck %s
; mem2reg is allowed with arbitrary atomic operations (although we only support
; it for atomic load and store at the moment).
define i32 @test1(i32 %x) {
; CHECK: @test1
; CHECK: ret i32 %x
%a = alloca i32
store atomic i32 %x, i32* %a seq_cst, align 4
%r = load atomic i32* %a seq_cst, align 4
ret i32 %r
}