From: Keno Fischer <kfischer@college.harvard.edu>
Date: Wed, 20 Aug 2014 19:00:37 +0000 (+0000)
Subject: Do not insert a tail call when returning multiple values on X86
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4b1cddbaf030af33fc25259b4afefb56141a8a59;p=oota-llvm.git

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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216117 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index af8e1a18808..9cb9e6abbef 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -2052,6 +2052,13 @@ bool X86TargetLowering::isUsedByReturnOnly(SDNode *N, SDValue &Chain) const {
        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;
   }
 
diff --git a/test/CodeGen/X86/tailcall-multiret.ll b/test/CodeGen/X86/tailcall-multiret.ll
new file mode 100644
index 00000000000..a77a59cd70b
--- /dev/null
+++ b/test/CodeGen/X86/tailcall-multiret.ll
@@ -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
+}