[PATCH] D107666: [OpenMP] Fix accidental reuse of VLA size

[Roger Ferrer Ibanez via Phabricator via cfe-commits]

rogfer01 created this revision.
rogfer01 added a reviewer: ABataev.
Herald added subscribers: guansong, yaxunl.
rogfer01 requested review of this revision.
Herald added a reviewer: jdoerfert.
Herald added subscribers: cfe-commits, sstefan1.
Herald added a project: clang.

We were using an `OpaqueValueExpr` allocated on the stack to store the size of a VLA. Because the `VLASizeMap` in `CodegenFunction` uses the address of the expression to avoid recomputing VLAs, we were accidentally reusing an earlier `llvm::Value`. This led to invalid LLVM IR.

After this change, we allocate the `OpaqueValueExpr` in `ASTContext` rather than in the stack. This is a temporary solution until `VLASizeMap` can be pushed and popped based on the context.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D107666

Files:
  clang/lib/CodeGen/CGOpenMPRuntime.cpp
  clang/test/OpenMP/vla_iterator_cache_bug.c


Index: clang/test/OpenMP/vla_iterator_cache_bug.c
===================================================================
--- /dev/null
+++ clang/test/OpenMP/vla_iterator_cache_bug.c
@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 -verify -fopenmp -x c++ -triple x86_64-unknown-linux-gnu \
+// RUN:   -emit-llvm %s -o - | FileCheck %s
+
+// expected-no-diagnostics
+
+extern int bounds1(int);
+extern int bounds2(int);
+
+extern void fun2(int n, int *a, int *b);
+extern void fun3(int n, int *a, int *b);
+
+void fun1(int n, int *a, int *b)
+{
+#pragma omp task depend(iterator(j = 0 : bounds1(n)), in : a[b[j]])
+  {
+    fun2(n, a, b);
+  }
+// CHECK: alloca %struct.kmp_depend_info, i64 [[FIRST_VLA:%.*]], align 16
+
+#pragma omp task depend(iterator(j = 0 : bounds2(n)), in : a[b[j]])
+  {
+    fun3(n, a, b);
+  }
+// CHECK-NOT: alloca %struct.kmp_depend_info, i64 [[FIRST_VLA]], align 16
+}
Index: clang/lib/CodeGen/CGOpenMPRuntime.cpp
===================================================================
--- clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -4400,14 +4400,14 @@
     if (NumOfElements) {
       NumOfElements = CGF.Builder.CreateNUWAdd(
           llvm::ConstantInt::get(CGF.SizeTy, NumAffinities), NumOfElements);
-      OpaqueValueExpr OVE(
+      auto *OVE = new (C) OpaqueValueExpr(
           Loc,
           C.getIntTypeForBitwidth(C.getTypeSize(C.getSizeType()), /*Signed=*/0),
           VK_PRValue);
-      CodeGenFunction::OpaqueValueMapping OpaqueMap(CGF, &OVE,
+      CodeGenFunction::OpaqueValueMapping OpaqueMap(CGF, OVE,
                                                     RValue::get(NumOfElements));
       KmpTaskAffinityInfoArrayTy =
-          C.getVariableArrayType(KmpTaskAffinityInfoTy, &OVE, ArrayType::Normal,
+          C.getVariableArrayType(KmpTaskAffinityInfoTy, OVE, ArrayType::Normal,
                                  /*IndexTypeQuals=*/0, SourceRange(Loc, Loc));
       // Properly emit variable-sized array.
       auto *PD = ImplicitParamDecl::Create(C, KmpTaskAffinityInfoArrayTy,
@@ -4898,13 +4898,13 @@
       NumOfElements =
           CGF.Builder.CreateNUWAdd(NumOfRegularWithIterators, NumOfElements);
     }
-    OpaqueValueExpr OVE(Loc,
-                        C.getIntTypeForBitwidth(/*DestWidth=*/64, /*Signed=*/0),
-                        VK_PRValue);
-    CodeGenFunction::OpaqueValueMapping OpaqueMap(CGF, &OVE,
+    auto *OVE = new (C) OpaqueValueExpr(
+        Loc, C.getIntTypeForBitwidth(/*DestWidth=*/64, /*Signed=*/0),
+        VK_PRValue);
+    CodeGenFunction::OpaqueValueMapping OpaqueMap(CGF, OVE,
                                                   RValue::get(NumOfElements));
     KmpDependInfoArrayTy =
-        C.getVariableArrayType(KmpDependInfoTy, &OVE, ArrayType::Normal,
+        C.getVariableArrayType(KmpDependInfoTy, OVE, ArrayType::Normal,
                                /*IndexTypeQuals=*/0, SourceRange(Loc, Loc));
     // CGF.EmitVariablyModifiedType(KmpDependInfoArrayTy);
     // Properly emit variable-sized array.


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