Author: lattner
Date: Mon Feb 18 00:12:38 2008
New Revision: 47258
URL: http://llvm.org/viewvc/llvm-project?rev=47258&view=rev
Log:
optimize away stackrestore calls that have no intervening alloca or call.
Modified:
llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
llvm/trunk/test/Transforms/InstCombine/stacksaverestore.ll
Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=47258&r1=47257&r2=47258&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Mon Feb 18
00:12:38 2008
@@ -8199,22 +8199,30 @@
}
}
- // 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;
}
}
Modified: llvm/trunk/test/Transforms/InstCombine/stacksaverestore.ll
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/stacksaverestore.ll?rev=47258&r1=47257&r2=47258&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/stacksaverestore.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/stacksaverestore.ll Mon Feb 18
00:12:38 2008
@@ -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 @@
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)
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