[llvm] r262095 - [InstCombine] Be more conservative about removing stackrestore
Reid Kleckner via llvm-commits
llvm-commits at lists.llvm.org
Fri Feb 26 16:53:55 PST 2016
Author: rnk
Date: Fri Feb 26 18:53:54 2016
New Revision: 262095
URL: http://llvm.org/viewvc/llvm-project?rev=262095&view=rev
Log:
[InstCombine] Be more conservative about removing stackrestore
We ended up removing a save/restore pair around an inalloca call,
leading to a miscompile in Chromium.
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
llvm/trunk/test/Transforms/InstCombine/stacksaverestore.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=262095&r1=262094&r2=262095&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Fri Feb 26 18:53:54 2016
@@ -1821,7 +1821,13 @@ Instruction *InstCombiner::visitCallInst
// If there is a stackrestore below this one, remove this one.
if (II->getIntrinsicID() == Intrinsic::stackrestore)
return eraseInstFromFunction(CI);
- // Otherwise, ignore the intrinsic.
+
+ // Bail if we cross over an intrinsic with side effects, such as
+ // llvm.stacksave, llvm.read_register, or llvm.setjmp.
+ if (II->mayHaveSideEffects()) {
+ CannotRemove = true;
+ break;
+ }
} else {
// If we found a non-intrinsic call, we can't remove the stack
// restore.
Modified: llvm/trunk/test/Transforms/InstCombine/stacksaverestore.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/stacksaverestore.ll?rev=262095&r1=262094&r2=262095&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/stacksaverestore.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/stacksaverestore.ll Fri Feb 26 18:53:54 2016
@@ -1,4 +1,6 @@
-; RUN: opt < %s -instcombine -S | grep "call.*stackrestore" | count 1
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+ at glob = global i32 0
declare i8* @llvm.stacksave()
declare void @llvm.stackrestore(i8*)
@@ -11,11 +13,19 @@ define i32* @test1(i32 %P) {
ret i32* %A
}
+; CHECK-LABEL: define i32* @test1(
+; CHECK-NOT: call void @llvm.stackrestore
+; CHECK: ret i32*
+
define void @test2(i8* %X) {
call void @llvm.stackrestore( i8* %X ) ;; no allocas before return.
ret void
}
+; CHECK-LABEL: define void @test2(
+; CHECK-NOT: call void @llvm.stackrestore
+; CHECK: ret void
+
define void @foo(i32 %size) nounwind {
entry:
%tmp118124 = icmp sgt i32 %size, 0 ; <i1> [#uses=1]
@@ -52,5 +62,51 @@ return: ; preds = %bb, %entry
ret void
}
+; CHECK-LABEL: define void @foo(
+; CHECK: %tmp = call i8* @llvm.stacksave()
+; CHECK: alloca i8
+; CHECK-NOT: stacksave
+; CHECK: call void @bar(
+; CHECK-NEXT: call void @llvm.stackrestore(i8* %tmp)
+; CHECK: ret void
+
declare void @bar(i32, i8*, i8*, i8*, i8*, i32)
+declare void @inalloca_callee(i32* inalloca)
+
+define void @test3(i32 %c) {
+entry:
+ br label %loop
+
+loop:
+ %i = phi i32 [0, %entry], [%i1, %loop]
+ %save1 = call i8* @llvm.stacksave()
+ %argmem = alloca inalloca i32
+ store i32 0, i32* %argmem
+ call void @inalloca_callee(i32* inalloca %argmem)
+
+ ; This restore cannot be deleted, the restore below does not make it dead.
+ call void @llvm.stackrestore(i8* %save1)
+
+ ; FIXME: We should be able to remove this save/restore pair, but we don't.
+ %save2 = call i8* @llvm.stacksave()
+ store i32 0, i32* @glob
+ call void @llvm.stackrestore(i8* %save2)
+ %i1 = add i32 1, %i
+ %done = icmp eq i32 %i1, %c
+ br i1 %done, label %loop, label %return
+
+return:
+ ret void
+}
+
+; CHECK-LABEL: define void @test3(
+; CHECK: loop:
+; CHECK: %i = phi i32 [ 0, %entry ], [ %i1, %loop ]
+; CHECK: %save1 = call i8* @llvm.stacksave()
+; CHECK: %argmem = alloca inalloca i32
+; CHECK: store i32 0, i32* %argmem
+; CHECK: call void @inalloca_callee(i32* inalloca {{.*}} %argmem)
+; CHECK: call void @llvm.stackrestore(i8* %save1)
+; CHECK: br i1 %done, label %loop, label %return
+; CHECK: ret void
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