[llvm-commits] [PATCH] ARM: Custom lower v2f32 = fp_round to fix crash with NEON

[David Peixotto]

Hi Pete,

 

Thanks for fixing this bug! I have a few minor comments on the patch below.

Index: lib/Target/ARM/ARMISelLowering.cpp

===================================================================

--- lib/Target/ARM/ARMISelLowering.cpp            (revision 167913)

+++ lib/Target/ARM/ARMISelLowering.cpp         (working copy)

+SDValue ARMTargetLowering::LowerFP_ROUND(SDValue Op, SelectionDAG &DAG)
const {

+  assert(Op.getValueType() == MVT::v2f32 &&

+         "FP_ROUND custom lowering should only occur for v2f32.");

+

+  DebugLoc DL = Op.getDebugLoc();

+  SmallVector<SDValue, 2> Vals;

 

I think a fixed size array would work fine here. It is preferred over
SmallVector in the llvm programmers manual:
http://llvm.org/docs/ProgrammersManual.html#ds_sequential

 

+  for(unsigned i = 0; i < 2; i++) {

+    SDValue Val = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, MVT::f64,

+                              Op.getOperand(0), DAG.getConstant(i,
MVT::i32));

+    Vals.push_back(DAG.getNode(ISD::FP_ROUND, DL, MVT::f32,

+                               Val, DAG.getIntPtrConstant(0)));

+  }

+  EVT VecVT = EVT::getVectorVT(*DAG.getContext(), MVT::f32, 2);

+  return DAG.getNode(ISD::BUILD_VECTOR, DL, VecVT, &Vals[0], 2);

+}

+

 

Index: test/CodeGen/ARM/neon_fpconv.ll

===================================================================

--- test/CodeGen/ARM/neon_fpconv.ll                (revision 0)

+++ test/CodeGen/ARM/neon_fpconv.ll             (revision 0)

@@ -0,0 +1,9 @@

+; RUN: llc < %s -march=arm -mattr=+neon | FileCheck %s

 

Please add a comment that this test is for PR12540.

 

+

+define <2 x float> @vtrunc(<2 x double> %a) {

+; CHECK: vcvt.f32.f64 [[S0:s[0-9]+]], [[D0:d[0-9]+]]

+; CHECK: vcvt.f32.f64 [[S1:s[0-9]+]], [[D1:d[0-9]+]]

+  %vt = fptrunc <2 x double> %a to <2 x float>

+  ret <2 x float> %vt

+}

+

 

Thanks,

David

 

-- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
by The Linux Foundation

 

 

From: llvm-commits-bounces at cs.uiuc.edu
[mailto:llvm-commits-bounces at cs.uiuc.edu] On Behalf Of Pete Couperus
Sent: Tuesday, November 13, 2012 11:24 PM
To: llvm-commits at cs.uiuc.edu
Subject: [llvm-commits] [PATCH] ARM: Custom lower v2f32 = fp_round to fix
crash with NEON

 

Hello,

Lowering "fptrunc <2 x double> %a to <2 x float>" is broken on ARM with
NEON.
This patch custom lowers this conversion using two single element vcvt's.
This fixes the following PRs.

http://llvm.org/bugs/show_bug.cgi?id=12540
http://llvm.org/bugs/show_bug.cgi?id=13964

Please review!
Thanks.

Pete

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