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optimize away stackrestore calls that have no intervening alloca or call.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47258 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -8199,22 +8199,30 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
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}
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}
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// If the stack restore is in a return/unwind block and if there are no
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// allocas or calls between the restore and the return, nuke the restore.
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TerminatorInst *TI = II->getParent()->getTerminator();
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if (isa<ReturnInst>(TI) || isa<UnwindInst>(TI)) {
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// Scan down this block to see if there is another stack restore in the
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// same block without an intervening call/alloca.
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BasicBlock::iterator BI = II;
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TerminatorInst *TI = II->getParent()->getTerminator();
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bool CannotRemove = false;
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for (++BI; &*BI != TI; ++BI) {
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if (isa<AllocaInst>(BI) ||
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(isa<CallInst>(BI) && !isa<IntrinsicInst>(BI))) {
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if (isa<AllocaInst>(BI)) {
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CannotRemove = true;
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break;
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}
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if (isa<CallInst>(BI)) {
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if (!isa<IntrinsicInst>(BI)) {
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CannotRemove = true;
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break;
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}
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if (!CannotRemove)
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// If there is a stackrestore below this one, remove this one.
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return EraseInstFromFunction(CI);
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}
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}
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// If the stack restore is in a return/unwind block and if there are no
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// allocas or calls between the restore and the return, nuke the restore.
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if (!CannotRemove && (isa<ReturnInst>(TI) || isa<UnwindInst>(TI)))
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return EraseInstFromFunction(CI);
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break;
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}
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}
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@ -1,4 +1,7 @@
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; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep {call.*stackrestore}
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; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {call.*stackrestore} | count 1
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declare i8* @llvm.stacksave()
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declare void @llvm.stackrestore(i8*)
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;; Test that llvm.stackrestore is removed when possible.
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define i32* @test1(i32 %P) {
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@ -13,7 +16,41 @@ define void @test2(i8* %X) {
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ret void
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}
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declare i8* @llvm.stacksave()
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define void @foo(i32 %size) nounwind {
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entry:
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%tmp118124 = icmp sgt i32 %size, 0 ; <i1> [#uses=1]
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br i1 %tmp118124, label %bb.preheader, label %return
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declare void @llvm.stackrestore(i8*)
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bb.preheader: ; preds = %entry
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%tmp25 = add i32 %size, -1 ; <i32> [#uses=1]
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%tmp125 = icmp slt i32 %size, 1 ; <i1> [#uses=1]
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%smax = select i1 %tmp125, i32 1, i32 %size ; <i32> [#uses=1]
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br label %bb
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bb: ; preds = %bb, %bb.preheader
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%i.0.reg2mem.0 = phi i32 [ 0, %bb.preheader ], [ %indvar.next, %bb ] ; <i32> [#uses=2]
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%tmp = call i8* @llvm.stacksave( ) ; <i8*> [#uses=1]
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%tmp23 = alloca i8, i32 %size ; <i8*> [#uses=2]
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%tmp27 = getelementptr i8* %tmp23, i32 %tmp25 ; <i8*> [#uses=1]
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store i8 0, i8* %tmp27, align 1
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%tmp28 = call i8* @llvm.stacksave( ) ; <i8*> [#uses=1]
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%tmp52 = alloca i8, i32 %size ; <i8*> [#uses=1]
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%tmp53 = call i8* @llvm.stacksave( ) ; <i8*> [#uses=1]
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%tmp77 = alloca i8, i32 %size ; <i8*> [#uses=1]
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%tmp78 = call i8* @llvm.stacksave( ) ; <i8*> [#uses=1]
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%tmp102 = alloca i8, i32 %size ; <i8*> [#uses=1]
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call void @bar( i32 %i.0.reg2mem.0, i8* %tmp23, i8* %tmp52, i8* %tmp77, i8* %tmp102, i32 %size ) nounwind
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call void @llvm.stackrestore( i8* %tmp78 )
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call void @llvm.stackrestore( i8* %tmp53 )
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call void @llvm.stackrestore( i8* %tmp28 )
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call void @llvm.stackrestore( i8* %tmp )
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%indvar.next = add i32 %i.0.reg2mem.0, 1 ; <i32> [#uses=2]
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%exitcond = icmp eq i32 %indvar.next, %smax ; <i1> [#uses=1]
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br i1 %exitcond, label %return, label %bb
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return: ; preds = %bb, %entry
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ret void
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}
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declare void @bar(i32, i8*, i8*, i8*, i8*, i32)
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