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[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.

llvm-svn: 262095
This commit is contained in:
Reid Kleckner 2016-02-27 00:53:54 +00:00
parent f91b163950
commit 892ae2e2b6
2 changed files with 64 additions and 2 deletions
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8
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
View File

@ -1821,7 +1821,13 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
// 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.

58
llvm/test/Transforms/InstCombine/stacksaverestore.ll
View File

@ -1,4 +1,6 @@
; RUN: opt < %s -instcombine -S | grep "call.*stackrestore" | count 1
; RUN: opt < %s -instcombine -S | FileCheck %s
@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