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More than just loads can read from memory: readonly calls like strlen 

also need to be checked for memory modifying instructions before we
can sink them.  THis fixes the second half of PR2297.

llvm-svn: 50860
This commit is contained in:
Chris Lattner 2008-05-08 17:37:37 +00:00
parent 4fa09669d8
commit 49a594e6ab
2 changed files with 32 additions and 4 deletions
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8
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -11229,8 +11229,8 @@ static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) {
// We can only sink load instructions if there is nothing between the load and // We can only sink load instructions if there is nothing between the load and
// the end of block that could change the value. // the end of block that could change the value.
if (LoadInst *LI = dyn_cast<LoadInst>(I)) { if (I->mayReadFromMemory()) {
for (BasicBlock::iterator Scan = LI, E = LI->getParent()->end(); for (BasicBlock::iterator Scan = I, E = I->getParent()->end();
Scan != E; ++Scan) Scan != E; ++Scan)
if (Scan->mayWriteToMemory()) if (Scan->mayWriteToMemory())
return false; return false;
@ -11388,8 +11388,8 @@ bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
} }
// See if we can trivially sink this instruction to a successor basic block. // See if we can trivially sink this instruction to a successor basic block.
// FIXME: Remove GetResultInst test when first class support for aggregates is // FIXME: Remove GetResultInst test when first class support for aggregates
// implemented. // is implemented.
if (I->hasOneUse() && !isa<GetResultInst>(I)) { if (I->hasOneUse() && !isa<GetResultInst>(I)) {
BasicBlock *BB = I->getParent(); BasicBlock *BB = I->getParent();
BasicBlock *UserParent = cast<Instruction>(I->use_back())->getParent(); BasicBlock *UserParent = cast<Instruction>(I->use_back())->getParent();

28
llvm/test/Transforms/InstCombine/2008-05-08-StrLenSink.ll Normal file
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@ -0,0 +1,28 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | %prcontext strlen 1 | not grep ret
; PR2297
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i386-apple-darwin8"
define i32 @a() nounwind {
entry:
%"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0]
%tmp1 = call i8* @malloc( i32 10 ) nounwind ; <i8*> [#uses=5]
%tmp3 = getelementptr i8* %tmp1, i32 1 ; <i8*> [#uses=1]
store i8 0, i8* %tmp3, align 1
%tmp5 = getelementptr i8* %tmp1, i32 0 ; <i8*> [#uses=1]
store i8 1, i8* %tmp5, align 1
%tmp7 = call i32 @strlen( i8* %tmp1 ) nounwind readonly ; <i32> [#uses=1]
%tmp9 = getelementptr i8* %tmp1, i32 0 ; <i8*> [#uses=1]
store i8 0, i8* %tmp9, align 1
%tmp11 = call i32 (...)* @b( i8* %tmp1 ) nounwind ; <i32> [#uses=0]
br label %return
return: ; preds = %entry
ret i32 %tmp7
}
declare i8* @malloc(i32) nounwind
declare i32 @strlen(i8*) nounwind readonly
declare i32 @b(...)