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optimize away stackrestore calls that have no intervening alloca or call.

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llvm-svn: 47258
This commit is contained in:
Chris Lattner 2008-02-18 06:12:38 +00:00
parent dd489bf3eb
commit 9851db050b
2 changed files with 58 additions and 13 deletions
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28
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -8199,22 +8199,30 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
}
}
// If the stack restore is in a return/unwind block and if there are no
// allocas or calls between the restore and the return, nuke the restore.
// Scan down this block to see if there is another stack restore in the
// same block without an intervening call/alloca.
BasicBlock::iterator BI = II;
TerminatorInst *TI = II->getParent()->getTerminator();
if (isa<ReturnInst>(TI) || isa<UnwindInst>(TI)) {
BasicBlock::iterator BI = II;
bool CannotRemove = false;
for (++BI; &*BI != TI; ++BI) {
if (isa<AllocaInst>(BI) ||
(isa<CallInst>(BI) && !isa<IntrinsicInst>(BI))) {
bool CannotRemove = false;
for (++BI; &*BI != TI; ++BI) {
if (isa<AllocaInst>(BI)) {
CannotRemove = true;
break;
}
if (isa<CallInst>(BI)) {
if (!isa<IntrinsicInst>(BI)) {
CannotRemove = true;
break;
}
}
if (!CannotRemove)
// If there is a stackrestore below this one, remove this one.
return EraseInstFromFunction(CI);
}
}
// If the stack restore is in a return/unwind block and if there are no
// allocas or calls between the restore and the return, nuke the restore.
if (!CannotRemove && (isa<ReturnInst>(TI) || isa<UnwindInst>(TI)))
return EraseInstFromFunction(CI);
break;
}
}

43
test/Transforms/InstCombine/stacksaverestore.ll
View File

@ -1,4 +1,7 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep {call.*stackrestore}
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {call.*stackrestore} | count 1
declare i8* @llvm.stacksave()
declare void @llvm.stackrestore(i8*)
;; Test that llvm.stackrestore is removed when possible.
define i32* @test1(i32 %P) {
@ -13,7 +16,41 @@ define void @test2(i8* %X) {
ret void
}
declare i8* @llvm.stacksave()
define void @foo(i32 %size) nounwind {
entry:
%tmp118124 = icmp sgt i32 %size, 0 ; <i1> [#uses=1]
br i1 %tmp118124, label %bb.preheader, label %return
declare void @llvm.stackrestore(i8*)
bb.preheader: ; preds = %entry
%tmp25 = add i32 %size, -1 ; <i32> [#uses=1]
%tmp125 = icmp slt i32 %size, 1 ; <i1> [#uses=1]
%smax = select i1 %tmp125, i32 1, i32 %size ; <i32> [#uses=1]
br label %bb
bb: ; preds = %bb, %bb.preheader
%i.0.reg2mem.0 = phi i32 [ 0, %bb.preheader ], [ %indvar.next, %bb ] ; <i32> [#uses=2]
%tmp = call i8* @llvm.stacksave( ) ; <i8*> [#uses=1]
%tmp23 = alloca i8, i32 %size ; <i8*> [#uses=2]
%tmp27 = getelementptr i8* %tmp23, i32 %tmp25 ; <i8*> [#uses=1]
store i8 0, i8* %tmp27, align 1
%tmp28 = call i8* @llvm.stacksave( ) ; <i8*> [#uses=1]
%tmp52 = alloca i8, i32 %size ; <i8*> [#uses=1]
%tmp53 = call i8* @llvm.stacksave( ) ; <i8*> [#uses=1]
%tmp77 = alloca i8, i32 %size ; <i8*> [#uses=1]
%tmp78 = call i8* @llvm.stacksave( ) ; <i8*> [#uses=1]
%tmp102 = alloca i8, i32 %size ; <i8*> [#uses=1]
call void @bar( i32 %i.0.reg2mem.0, i8* %tmp23, i8* %tmp52, i8* %tmp77, i8* %tmp102, i32 %size ) nounwind
call void @llvm.stackrestore( i8* %tmp78 )
call void @llvm.stackrestore( i8* %tmp53 )
call void @llvm.stackrestore( i8* %tmp28 )
call void @llvm.stackrestore( i8* %tmp )
%indvar.next = add i32 %i.0.reg2mem.0, 1 ; <i32> [#uses=2]
%exitcond = icmp eq i32 %indvar.next, %smax ; <i1> [#uses=1]
br i1 %exitcond, label %return, label %bb
return: ; preds = %bb, %entry
ret void
}
declare void @bar(i32, i8*, i8*, i8*, i8*, i32)