Merging r326376:

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r326376 | jdevlieghere | 2018-02-28 14:28:44 -0800 (Wed, 28 Feb 2018) | 12 lines

[GlobalOpt] don't change CC of musttail calle(e|r)

When the function has musttail call - its cc is fixed to be equal to the
cc of the musttail callee. In such case (and in the case of the musttail
callee), GlobalOpt should not change the cc to fastcc as it will break
the invariant.

This fixes PR36546

Patch by: Fedor Indutny (indutny)

Differential revision: https://reviews.llvm.org/D43859
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_60@329634 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/IPO/GlobalOpt.cpp b/lib/Transforms/IPO/GlobalOpt.cpp
index 4bb2984e3b47328613700193c3ae838c85963e0f..e0bbf45d316aaf0b6cca9720829810e0970d8e86 100644 (file)
--- a/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/lib/Transforms/IPO/GlobalOpt.cpp
@@ -2099,8 +2099,31 @@ static void RemoveNestAttribute(Function *F) {
 /// GHC, or anyregcc.
 static bool isProfitableToMakeFastCC(Function *F) {
   CallingConv::ID CC = F->getCallingConv();
+
   // FIXME: Is it worth transforming x86_stdcallcc and x86_fastcallcc?
-  return CC == CallingConv::C || CC == CallingConv::X86_ThisCall;
+  if (CC != CallingConv::C && CC != CallingConv::X86_ThisCall)
+    return false;
+
+  // FIXME: Change CC for the whole chain of musttail calls when possible.
+  //
+  // Can't change CC of the function that either has musttail calls, or is a
+  // musttail callee itself
+  for (User *U : F->users()) {
+    if (isa<BlockAddress>(U))
+      continue;
+    CallInst* CI = dyn_cast<CallInst>(U);
+    if (!CI)
+      continue;
+
+    if (CI->isMustTailCall())
+      return false;
+  }
+
+  for (BasicBlock &BB : *F)
+    if (BB.getTerminatingMustTailCall())
+      return false;
+
+  return true;
 }
 
 static bool

diff --git a/test/Transforms/GlobalOpt/musttail_cc.ll b/test/Transforms/GlobalOpt/musttail_cc.ll
new file mode 100644 (file)
index 0000000..fc927ea
--- /dev/null
+++ b/test/Transforms/GlobalOpt/musttail_cc.ll
@@ -0,0 +1,34 @@
+; RUN: opt < %s -globalopt -S | FileCheck %s
+; PR36546
+
+; Check that musttail callee preserves its calling convention
+
+define i32 @test(i32 %a) {
+  ; CHECK: %ca = musttail call i32 @foo(i32 %a)
+  %ca = musttail call i32 @foo(i32 %a)
+  ret i32 %ca
+}
+
+; CHECK-LABEL: define internal i32 @foo(i32 %a)
+define internal i32 @foo(i32 %a) {
+  ret i32 %a
+}
+
+; Check that musttail caller preserves its calling convention
+
+define i32 @test2(i32 %a) {
+  %ca = call i32 @foo1(i32 %a)
+  ret i32 %ca
+}
+
+; CHECK-LABEL: define internal i32 @foo1(i32 %a)
+define internal i32 @foo1(i32 %a) {
+  ; CHECK: %ca = musttail call i32 @foo2(i32 %a)
+  %ca = musttail call i32 @foo2(i32 %a)
+  ret i32 %ca
+}
+
+; CHECK-LABEL: define internal i32 @foo2(i32 %a)
+define internal i32 @foo2(i32 %a) {
+  ret i32 %a
+}