r355054 - [CodeGen] Fix some broken IR generated by -fsanitize=unsigned-integer-overflow

[Erik Pilkington via cfe-commits]

Author: epilk
Date: Wed Feb 27 16:47:55 2019
New Revision: 355054

URL: http://llvm.org/viewvc/llvm-project?rev=355054&view=rev
Log:
[CodeGen] Fix some broken IR generated by -fsanitize=unsigned-integer-overflow

I think the author of the function assumed that `GetInsertBlock()`
wouldn't change from where `atomicPHI` was created, but this isn't
true when `-fsanitize=unsigned-integer-overflow` is enabled (we
generate an overflow/continuation label). Fix by keeping track of the
block we want to return to to complete the cmpxchg loop.

rdar://48406558

Differential revision: https://reviews.llvm.org/D58744

Added:
    cfe/trunk/test/CodeGen/sanitize-atomic-int-overflow.c
Modified:
    cfe/trunk/lib/CodeGen/CGExprScalar.cpp

Modified: cfe/trunk/lib/CodeGen/CGExprScalar.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExprScalar.cpp?rev=355054&r1=355053&r2=355054&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGExprScalar.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGExprScalar.cpp Wed Feb 27 16:47:55 2019
@@ -2555,14 +2555,14 @@ ScalarExprEmitter::EmitScalarPrePostIncD
   }
 
   if (atomicPHI) {
-    llvm::BasicBlock *opBB = Builder.GetInsertBlock();
+    llvm::BasicBlock *curBlock = Builder.GetInsertBlock();
     llvm::BasicBlock *contBB = CGF.createBasicBlock("atomic_cont", CGF.CurFn);
     auto Pair = CGF.EmitAtomicCompareExchange(
         LV, RValue::get(atomicPHI), RValue::get(value), E->getExprLoc());
     llvm::Value *old = CGF.EmitToMemory(Pair.first.getScalarVal(), type);
     llvm::Value *success = Pair.second;
-    atomicPHI->addIncoming(old, opBB);
-    Builder.CreateCondBr(success, contBB, opBB);
+    atomicPHI->addIncoming(old, curBlock);
+    Builder.CreateCondBr(success, contBB, atomicPHI->getParent());
     Builder.SetInsertPoint(contBB);
     return isPre ? value : input;
   }
@@ -2909,14 +2909,14 @@ LValue ScalarExprEmitter::EmitCompoundAs
                                 Loc, ScalarConversionOpts(CGF.SanOpts));
 
   if (atomicPHI) {
-    llvm::BasicBlock *opBB = Builder.GetInsertBlock();
+    llvm::BasicBlock *curBlock = Builder.GetInsertBlock();
     llvm::BasicBlock *contBB = CGF.createBasicBlock("atomic_cont", CGF.CurFn);
     auto Pair = CGF.EmitAtomicCompareExchange(
         LHSLV, RValue::get(atomicPHI), RValue::get(Result), E->getExprLoc());
     llvm::Value *old = CGF.EmitToMemory(Pair.first.getScalarVal(), LHSTy);
     llvm::Value *success = Pair.second;
-    atomicPHI->addIncoming(old, opBB);
-    Builder.CreateCondBr(success, contBB, opBB);
+    atomicPHI->addIncoming(old, curBlock);
+    Builder.CreateCondBr(success, contBB, atomicPHI->getParent());
     Builder.SetInsertPoint(contBB);
     return LHSLV;
   }

Added: cfe/trunk/test/CodeGen/sanitize-atomic-int-overflow.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/sanitize-atomic-int-overflow.c?rev=355054&view=auto
==============================================================================
--- cfe/trunk/test/CodeGen/sanitize-atomic-int-overflow.c (added)
+++ cfe/trunk/test/CodeGen/sanitize-atomic-int-overflow.c Wed Feb 27 16:47:55 2019
@@ -0,0 +1,33 @@
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.14.0 -fsanitize=unsigned-integer-overflow %s -emit-llvm -o - | FileCheck %s
+
+_Atomic(unsigned) atomic;
+
+// CHECK-LABEL: define void @cmpd_assign
+void cmpd_assign() {
+  // CHECK: br label %[[LOOP_START:.*]]
+
+  // CHECK: [[LOOP_START]]:
+  // CHECK-NEXT: phi i32 {{.*}}, [ {{.*}}, %[[INCOMING_BLOCK:.*]] ]
+
+  // CHECK: [[INCOMING_BLOCK]]:
+  // CHECK-NEXT: cmpxchg
+  // CHECK-NEXT: extractvalue
+  // CHECK-NEXT: extractvalue
+  // CHECK-NEXT: br i1 %8, label %{{.*}}, label %[[LOOP_START]]
+  atomic += 1;
+}
+
+// CHECK-LABEL: define void @inc
+void inc() {
+  // CHECK: br label %[[LOOP_START:.*]]
+
+  // CHECK: [[LOOP_START]]:
+  // CHECK-NEXT: phi i32 {{.*}}, [ {{.*}}, %[[INCOMING_BLOCK:.*]] ]
+
+  // CHECK: [[INCOMING_BLOCK]]:
+  // CHECK-NEXT: cmpxchg
+  // CHECK-NEXT: extractvalue
+  // CHECK-NEXT: extractvalue
+  // CHECK-NEXT: br i1 %8, label %{{.*}}, label %[[LOOP_START]]
+  atomic++;
+}