[PATCH] D12400: Fix store detection for return value in CGCall

[Jakub Kuderski via cfe-commits]

kuhar created this revision.
kuhar added a subscriber: cfe-commits.
kuhar set the repository for this revision to rL LLVM.
Herald added subscribers: srhines, danalbert, tberghammer.

`findDominatingStoreToReturn` in CGCall.cpp didn't check if a candidate store instruction used the ReturnValue as pointer operand or value operand. This led to wrong code gen - in later stages (load-store elision code) the found store and its operand would be erased, causing ReturnValue to become a <badref>.

The patch adds a check that makes sure that ReturnValue is a pointer operand of store instruction. Regression test is also added.

This fixes PR24386.

Repository:
  rL LLVM

http://reviews.llvm.org/D12400

Files:
  lib/CodeGen/CGCall.cpp
  test/CodeGen/arm_function_epilog.cpp

Index: test/CodeGen/arm_function_epilog.cpp
===================================================================
--- /dev/null
+++ test/CodeGen/arm_function_epilog.cpp
@@ -0,0 +1,17 @@
+// REQUIRES: arm-registered-target
+// RUN: %clang_cc1 -triple armv7-none-linux-androideabi -target-abi aapcs-linux -mfloat-abi hard -x c++ -emit-llvm %s -o - | FileCheck %s
+
+struct Vec2 {
+    union { struct { float x, y; };
+            float data[2];
+    };
+};
+
+// CHECK: define arm_aapcs_vfpcc %struct.Vec2 @_Z7getVec2v()
+// CHECK: ret %struct.Vec2
+Vec2 getVec2() {
+    Vec2 out;
+    union { Vec2* v; unsigned char* u; } x;
+    x.v = &out;
+    return out;
+}
Index: lib/CodeGen/CGCall.cpp
===================================================================
--- lib/CodeGen/CGCall.cpp
+++ lib/CodeGen/CGCall.cpp
@@ -2329,6 +2329,7 @@
   llvm::StoreInst *store =
     dyn_cast<llvm::StoreInst>(CGF.ReturnValue->user_back());
   if (!store) return nullptr;
+  if (store->getPointerOperand() != CGF.ReturnValue) return nullptr;
 
   // These aren't actually possible for non-coerced returns, and we
   // only care about non-coerced returns on this code path.


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