[llvm] r216117 - Do not insert a tail call when returning multiple values on X86

[Keno Fischer]

Author: kfischer
Date: Wed Aug 20 14:00:37 2014
New Revision: 216117

URL: http://llvm.org/viewvc/llvm-project?rev=216117&view=rev
Log:
Do not insert a tail call when returning multiple values on X86

Summary: This fixes http://llvm.org/bugs/show_bug.cgi?id=19530.
The problem is that X86ISelLowering erroneously thought the third call
was eligible for tail call elimination.
It would have been if it's return value was actually the one returned
by the calling function, but here that is not the case and
additional values are being returned.

Test Plan: Test case from the original bug report is included.

Reviewers: rafael

Reviewed By: rafael

Subscribers: rafael, llvm-commits

Differential Revision: http://reviews.llvm.org/D4968

Added:
    llvm/trunk/test/CodeGen/X86/tailcall-multiret.ll
Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=216117&r1=216116&r2=216117&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Wed Aug 20 14:00:37 2014
@@ -2052,6 +2052,13 @@ bool X86TargetLowering::isUsedByReturnOn
        UI != UE; ++UI) {
     if (UI->getOpcode() != X86ISD::RET_FLAG)
       return false;
+    // If we are returning more than one value, we can definitely
+    // not make a tail call see PR19530
+    if (UI->getNumOperands() > 4)
+      return false;
+    if (UI->getNumOperands() == 4 &&
+        UI->getOperand(UI->getNumOperands()-1).getValueType() != MVT::Glue)
+      return false;
     HasRet = true;
   }
 

Added: llvm/trunk/test/CodeGen/X86/tailcall-multiret.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/tailcall-multiret.ll?rev=216117&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/tailcall-multiret.ll (added)
+++ llvm/trunk/test/CodeGen/X86/tailcall-multiret.ll Wed Aug 20 14:00:37 2014
@@ -0,0 +1,16 @@
+; RUN: llc < %s -mtriple=x86_64-linux-gnu -mcpu=core2 | FileCheck %s
+; See PR19530
+declare double    @llvm.powi.f64(double %Val, i32 %power)
+define <3 x double> @julia_foo17589(i32 %arg) {
+  %tmp1 = call double @llvm.powi.f64(double 1.000000e+00, i32 %arg)
+; CHECK: callq   __powidf2
+  %tmp2 = insertelement <3 x double> undef, double %tmp1, i32 0
+  %tmp3 = call double @llvm.powi.f64(double 2.000000e+00, i32 %arg)
+; CHECK: callq   __powidf2
+  %tmp4 = insertelement <3 x double> %tmp2, double %tmp3, i32 1
+  %tmp5 = call double @llvm.powi.f64(double 3.000000e+00, i32 %arg)
+; CHECK: callq   __powidf2
+  %tmp6 = insertelement <3 x double> %tmp4, double %tmp5, i32 2
+; CHECK-NOT: TAILCALL
+  ret <3 x double> %tmp6
+}