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Transform div to mul with reciprocal only when fp imm is legal.

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This fixes PR12516 and uncovers one weird problem in legalize (workarounded)

llvm-svn: 154394
This commit is contained in:
Anton Korobeynikov 2012-04-10 13:22:49 +00:00
parent a098752b13
commit 0fc5fe0430
2 changed files with 40 additions and 2 deletions
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11
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -5769,8 +5769,15 @@ SDValue DAGCombiner::visitFDIV(SDNode *N) {
APFloat N1APF = N1CFP->getValueAPF();
APFloat Recip(N1APF.getSemantics(), 1); // 1.0
APFloat::opStatus st = Recip.divide(N1APF, APFloat::rmNearestTiesToEven);
// Only do the transform if the reciprocal is not too horrible (eg not NaN).
if (st == APFloat::opOK || st == APFloat::opInexact)
// Only do the transform if the reciprocal is not too horrible (eg not NaN)
// and the reciprocal is a legal fp imm.
if ((st == APFloat::opOK || st == APFloat::opInexact) &&
(!LegalOperations ||
// FIXME: custom lowering of ConstantFP might fail (see e.g. ARM
// backend)... we should handle this gracefully after Legalize.
// TLI.isOperationLegalOrCustom(llvm::ISD::ConstantFP, VT) ||
TLI.isOperationLegal(llvm::ISD::ConstantFP, VT) ||
TLI.isFPImmLegal(Recip, VT)))
return DAG.getNode(ISD::FMUL, N->getDebugLoc(), VT, N0,
DAG.getConstantFP(Recip, VT));
}

31
test/CodeGen/ARM/2012-04-10-DAGCombine.ll Normal file
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@ -0,0 +1,31 @@
; RUN: llc < %s -march=arm -mcpu=cortex-a9 -enable-unsafe-fp-math
;target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:64:128-a0:0:64-n32-S64"
;target triple = "armv7-none-linux-gnueabi"
define arm_aapcs_vfpcc void @foo(<4 x float> %arg) nounwind align 2 {
bb4:
%tmp = extractelement <2 x float> undef, i32 0
br i1 undef, label %bb18, label %bb5
bb5: ; preds = %bb4
%tmp6 = fadd float %tmp, -1.500000e+01
%tmp7 = fdiv float %tmp6, 2.000000e+01
%tmp8 = fadd float %tmp7, 1.000000e+00
%tmp9 = fdiv float 1.000000e+00, %tmp8
%tmp10 = fsub float 1.000000e+00, %tmp9
%tmp11 = fmul float %tmp10, 1.000000e+01
%tmp12 = fadd float %tmp11, 1.500000e+01
%tmp13 = fdiv float %tmp12, %tmp
%tmp14 = insertelement <2 x float> undef, float %tmp13, i32 0
%tmp15 = shufflevector <2 x float> %tmp14, <2 x float> undef, <4 x i32> zeroinitializer
%tmp16 = fmul <4 x float> zeroinitializer, %tmp15
%tmp17 = fadd <4 x float> %tmp16, %arg
store <4 x float> %tmp17, <4 x float>* undef, align 8, !tbaa !0
br label %bb18
bb18: ; preds = %bb5, %bb4
ret void
}
!0 = metadata !{metadata !"omnipotent char", metadata !1}
!1 = metadata !{metadata !"Simple C/C++ TBAA", null}