[safestack] Sink unsafe address computation to each use.
This is a fix for PR27844.
When replacing uses of unsafe allocas, emit the new location
immediately after each use. Without this, the pointer stays live from
the function entry to the last use, while it's usually cheaper to
recalculate.
llvm-svn: 272969
diff --git a/llvm/lib/CodeGen/SafeStack.cpp b/llvm/lib/CodeGen/SafeStack.cpp
index 28f5ed8..457acb1 100644
--- a/llvm/lib/CodeGen/SafeStack.cpp
+++ b/llvm/lib/CodeGen/SafeStack.cpp
@@ -606,16 +606,39 @@
StaticOffset += Size;
StaticOffset = alignTo(StaticOffset, Align);
- Value *Off = IRB.CreateGEP(BasePointer, // BasePointer is i8*
- ConstantInt::get(Int32Ty, -StaticOffset));
- Value *NewAI = IRB.CreateBitCast(Off, AI->getType(), AI->getName());
- if (AI->hasName() && isa<Instruction>(NewAI))
- cast<Instruction>(NewAI)->takeName(AI);
-
- // Replace alloc with the new location.
replaceDbgDeclareForAlloca(AI, BasePointer, DIB, /*Deref=*/true, -StaticOffset);
replaceDbgValueForAlloca(AI, BasePointer, DIB, -StaticOffset);
- AI->replaceAllUsesWith(NewAI);
+
+ // Replace uses of the alloca with the new location.
+ // Insert address calculation close to each use to work around PR27844.
+ std::string Name = std::string(AI->getName()) + ".unsafe";
+ while (!AI->use_empty()) {
+ Use &U = *AI->use_begin();
+ Instruction *User = cast<Instruction>(U.getUser());
+
+ Instruction *InsertBefore;
+ if (auto *PHI = dyn_cast<PHINode>(User))
+ InsertBefore = PHI->getIncomingBlock(U)->getTerminator();
+ else
+ InsertBefore = User;
+
+ IRBuilder<> IRBUser(InsertBefore);
+ Value *Off = IRBUser.CreateGEP(BasePointer, // BasePointer is i8*
+ ConstantInt::get(Int32Ty, -StaticOffset));
+ Value *Replacement = IRBUser.CreateBitCast(Off, AI->getType(), Name);
+
+ if (auto *PHI = dyn_cast<PHINode>(User)) {
+ // PHI nodes may have multiple incoming edges from the same BB (why??),
+ // all must be updated at once with the same incoming value.
+ auto *BB = PHI->getIncomingBlock(U);
+ for (unsigned I = 0; I < PHI->getNumIncomingValues(); ++I)
+ if (PHI->getIncomingBlock(I) == BB)
+ PHI->setIncomingValue(I, Replacement);
+ } else {
+ U.set(Replacement);
+ }
+ }
+
AI->eraseFromParent();
}
diff --git a/llvm/test/Transforms/SafeStack/array-aligned.ll b/llvm/test/Transforms/SafeStack/array-aligned.ll
index 4676903..26558e4 100644
--- a/llvm/test/Transforms/SafeStack/array-aligned.ll
+++ b/llvm/test/Transforms/SafeStack/array-aligned.ll
@@ -13,16 +13,15 @@
; CHECK: store i8* %[[USST]], i8** @__safestack_unsafe_stack_ptr
- ; CHECK: %[[AADDR:.*]] = alloca i8*, align 8
%a.addr = alloca i8*, align 8
-
- ; CHECK: %[[BUFPTR:.*]] = getelementptr i8, i8* %[[USP]], i32 -16
- ; CHECK: %[[BUFPTR2:.*]] = bitcast i8* %[[BUFPTR]] to [16 x i8]*
%buf = alloca [16 x i8], align 16
+ ; CHECK: %[[AADDR:.*]] = alloca i8*, align 8
; CHECK: store i8* {{.*}}, i8** %[[AADDR]], align 8
store i8* %a, i8** %a.addr, align 8
+ ; CHECK: %[[BUFPTR:.*]] = getelementptr i8, i8* %[[USP]], i32 -16
+ ; CHECK: %[[BUFPTR2:.*]] = bitcast i8* %[[BUFPTR]] to [16 x i8]*
; CHECK: %[[GEP:.*]] = getelementptr inbounds [16 x i8], [16 x i8]* %[[BUFPTR2]], i32 0, i32 0
%gep = getelementptr inbounds [16 x i8], [16 x i8]* %buf, i32 0, i32 0
diff --git a/llvm/test/Transforms/SafeStack/array.ll b/llvm/test/Transforms/SafeStack/array.ll
index 564213e..7dcf7fa 100644
--- a/llvm/test/Transforms/SafeStack/array.ll
+++ b/llvm/test/Transforms/SafeStack/array.ll
@@ -17,16 +17,15 @@
; CHECK: store i8* %[[USST]], i8** @__safestack_unsafe_stack_ptr
- ; CHECK: %[[AADDR:.*]] = alloca i8*, align 8
%a.addr = alloca i8*, align 8
-
- ; CHECK: %[[BUFPTR:.*]] = getelementptr i8, i8* %[[USP]], i32 -4
- ; CHECK: %[[BUFPTR2:.*]] = bitcast i8* %[[BUFPTR]] to [4 x i8]*
%buf = alloca [4 x i8], align 1
+ ; CHECK: %[[AADDR:.*]] = alloca i8*, align 8
; CHECK: store i8* {{.*}}, i8** %[[AADDR]], align 8
store i8* %a, i8** %a.addr, align 8
+ ; CHECK: %[[BUFPTR:.*]] = getelementptr i8, i8* %[[USP]], i32 -4
+ ; CHECK: %[[BUFPTR2:.*]] = bitcast i8* %[[BUFPTR]] to [4 x i8]*
; CHECK: %[[GEP:.*]] = getelementptr inbounds [4 x i8], [4 x i8]* %[[BUFPTR2]], i32 0, i32 0
%gep = getelementptr inbounds [4 x i8], [4 x i8]* %buf, i32 0, i32 0
diff --git a/llvm/test/Transforms/SafeStack/phi.ll b/llvm/test/Transforms/SafeStack/phi.ll
new file mode 100644
index 0000000..3ee56aa
--- /dev/null
+++ b/llvm/test/Transforms/SafeStack/phi.ll
@@ -0,0 +1,35 @@
+; RUN: opt -safe-stack -S -mtriple=i386-pc-linux-gnu < %s -o - | FileCheck %s
+; RUN: opt -safe-stack -S -mtriple=x86_64-pc-linux-gnu < %s -o - | FileCheck %s
+
+define void @f(i1 %d1, i1 %d2) safestack {
+entry:
+; CHECK-LABEL: define void @f(
+; CHECK: %[[USP:.*]] = load i8*, i8** @__safestack_unsafe_stack_ptr
+; CHECK-NEXT: getelementptr i8, i8* %[[USP]], i32 -16
+; CHECK: br i1 %d1, label %[[BB0:.*]], label %[[BB1:.*]]
+ %a = alloca i32, align 8
+ %b = alloca i32, align 8
+ br i1 %d1, label %bb0, label %bb1
+
+bb0:
+; CHECK: [[BB0]]:
+; CHECK: %[[Ai8:.*]] = getelementptr i8, i8* %unsafe_stack_ptr, i32
+; CHECK: %[[AUNSAFE:.*]] = bitcast i8* %[[Ai8]] to i32*
+; CHECK: br i1
+ br i1 %d2, label %bb2, label %bb2
+
+bb1:
+; CHECK: [[BB1]]:
+; CHECK: %[[Bi8:.*]] = getelementptr i8, i8* %unsafe_stack_ptr, i32
+; CHECK: %[[BUNSAFE:.*]] = bitcast i8* %[[Bi8]] to i32*
+; CHECK: br label
+ br label %bb2
+
+bb2:
+; CHECK: phi i32* [ %[[AUNSAFE]], %[[BB0]] ], [ %[[AUNSAFE]], %[[BB0]] ], [ %[[BUNSAFE]], %[[BB1]] ]
+ %c = phi i32* [ %a, %bb0 ], [ %a, %bb0 ], [ %b, %bb1 ]
+ call void @capture(i32* %c)
+ ret void
+}
+
+declare void @capture(i32*)
diff --git a/llvm/test/Transforms/SafeStack/sink-to-use.ll b/llvm/test/Transforms/SafeStack/sink-to-use.ll
new file mode 100644
index 0000000..e208ce1
--- /dev/null
+++ b/llvm/test/Transforms/SafeStack/sink-to-use.ll
@@ -0,0 +1,22 @@
+; Test that unsafe alloca address calculation is done immediately before each use.
+; RUN: opt -safe-stack -S -mtriple=x86_64-pc-linux-gnu < %s -o - | FileCheck %s
+; RUN: opt -safe-stack -S -mtriple=i386-pc-linux-gnu < %s -o - | FileCheck %s
+
+define void @f() safestack {
+entry:
+ %x0 = alloca i32, align 4
+ %x1 = alloca i32, align 4
+
+; CHECK: %[[A:.*]] = getelementptr i8, i8* %{{.*}}, i32 -4
+; CHECK: %[[X0:.*]] = bitcast i8* %[[A]] to i32*
+; CHECK: call void @use(i32* %[[X0]])
+ call void @use(i32* %x0)
+
+; CHECK: %[[B:.*]] = getelementptr i8, i8* %{{.*}}, i32 -8
+; CHECK: %[[X1:.*]] = bitcast i8* %[[B]] to i32*
+; CHECK: call void @use(i32* %[[X1]])
+ call void @use(i32* %x1)
+ ret void
+}
+
+declare void @use(i32*)
diff --git a/llvm/test/Transforms/SafeStack/struct.ll b/llvm/test/Transforms/SafeStack/struct.ll
index 12a0085..b64803d 100644
--- a/llvm/test/Transforms/SafeStack/struct.ll
+++ b/llvm/test/Transforms/SafeStack/struct.ll
@@ -15,16 +15,15 @@
; CHECK: store i8* %[[USST]], i8** @__safestack_unsafe_stack_ptr
- ; CHECK: %[[AADDR:.*]] = alloca i8*, align 8
%a.addr = alloca i8*, align 8
-
- ; CHECK: %[[BUFPTR:.*]] = getelementptr i8, i8* %[[USP]], i32 -16
- ; CHECK: %[[BUFPTR2:.*]] = bitcast i8* %[[BUFPTR]] to %struct.foo*
%buf = alloca %struct.foo, align 1
+ ; CHECK: %[[AADDR:.*]] = alloca i8*, align 8
; CHECK: store i8* {{.*}}, i8** %[[AADDR]], align 8
store i8* %a, i8** %a.addr, align 8
+ ; CHECK: %[[BUFPTR:.*]] = getelementptr i8, i8* %[[USP]], i32 -16
+ ; CHECK: %[[BUFPTR2:.*]] = bitcast i8* %[[BUFPTR]] to %struct.foo*
; CHECK: %[[GEP:.*]] = getelementptr inbounds %struct.foo, %struct.foo* %[[BUFPTR2]], i32 0, i32 0, i32 0
%gep = getelementptr inbounds %struct.foo, %struct.foo* %buf, i32 0, i32 0, i32 0