[PATCH] D33733: CGCleanup: No need to do domination fixups for static allocas

[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 make sure that domination fixup is not done static allocas.

(Alternative of https://reviews.llvm.org/D33663)


https://reviews.llvm.org/D33733

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
@@ -448,6 +448,11 @@
     auto *Inst = dyn_cast_or_null<llvm::Instruction>(*ReloadedValue);
     if (!Inst)
       continue;
+    // If it is a static alloca, no need to spill.
+    if (auto *AI = dyn_cast<llvm::AllocaInst>(Inst))
+      if (AI->isStaticAlloca())
+        continue;
+
     Address Tmp =
         CreateDefaultAlignTempAlloca(Inst->getType(), "tmp.exprcleanup");
 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D33733.100896.patch
Type: text/x-patch
Size: 1625 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20170531/3d9c5455/attachment.bin>