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Do not insert a tail call when returning multiple values on X86

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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
This commit is contained in:
Keno Fischer 2014-08-20 19:00:37 +00:00
parent 242320399f
commit 4b1cddbaf0
2 changed files with 23 additions and 0 deletions
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7
lib/Target/X86/X86ISelLowering.cpp
View File

@ -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;
}

16
test/CodeGen/X86/tailcall-multiret.ll Normal file
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@ -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
}