[PATCH] D33663: CGCleanup: Use correct insertion point for AllocaInst

[Gor Nishanov via Phabricator via cfe-commits]

GorNishanov created this revision.

This is a follow up for the https://reviews.llvm.org/rL297084 which made sure that dominance is preserved during expression cleanup emission.
We ran into a case where dominance fixup code was inserting the store in the middle of allocas.

  %x = alloca i32, align 4
  store i32* %x, i32** %tmp.exprcleanup, align 4 ; <===== HERE
  %ref.tmp3 = alloca %struct.A, align 1
  %agg.tmp5 = alloca %"struct.std::experimental::coroutines_v1::coroutine_handle.0", align 4
  %tmp.exprcleanup = alloca i32*, align 4
  %allocapt = bitcast i32 undef to i32
  store i32 %0, i32* %.addr, align 4

This fix makes sure that if we are fixing up domination for an alloca instruction we will do it after the AllocaInsertPt


https://reviews.llvm.org/D33663

Files:
  lib/CodeGen/CGCleanup.cpp
  test/CodeGenCoroutines/coro-await-domination.cpp


Index: test/CodeGenCoroutines/coro-await-domination.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCoroutines/coro-await-domination.cpp
@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fcoroutines-ts -std=c++14 -emit-llvm %s -o - | FileCheck %s
+#include "Inputs/coroutine.h"
+
+using namespace std::experimental;
+
+struct coro {
+  struct promise_type {
+    coro get_return_object();
+    suspend_never initial_suspend();
+    suspend_never final_suspend();
+    void return_void();
+    static void unhandled_exception();
+  };
+};
+
+struct A {
+  ~A();
+  bool await_ready();
+  int await_resume();
+  template <typename F> void await_suspend(F);
+};
+
+// Verifies that domination is properly built during cleanup.
+// Without CGCleanup.cpp fix verifier was reporting:
+// Instruction does not dominate all uses!
+//  %tmp.exprcleanup = alloca i32*, align 8
+//  store i32* %x, i32** %tmp.exprcleanup, align 8
+
+
+// CHECK-LABEL: f(
+extern "C" coro f(int) {
+  int x = 42;
+  x = co_await A{};
+}
Index: lib/CodeGen/CGCleanup.cpp
===================================================================
--- lib/CodeGen/CGCleanup.cpp
+++ lib/CodeGen/CGCleanup.cpp
@@ -455,6 +455,8 @@
     llvm::BasicBlock::iterator InsertBefore;
     if (auto *Invoke = dyn_cast<llvm::InvokeInst>(Inst))
       InsertBefore = Invoke->getNormalDest()->getFirstInsertionPt();
+    else if (isa<llvm::AllocaInst>(Inst))
+      InsertBefore = std::next(AllocaInsertPt->getIterator());
     else
       InsertBefore = std::next(Inst->getIterator());
     CGBuilderTy(CGM, &*InsertBefore).CreateStore(Inst, Tmp);


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