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Avoid creating BUILD_VECTOR of all zero elements of "non-normalized" type (e.g. v8i16 on x86) after legalizer. Instruction selection does not expect to see them. In all likelihood this can only be an issue in a bugpoint reduced test case.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48136 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2008-03-10 07:19:13 +00:00
parent 8d88dbcbae
commit f79e60649a
2 changed files with 28 additions and 0 deletions
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4
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -1103,6 +1103,10 @@ SDOperand DAGCombiner::visitSUB(SDNode *N) {
// fold (sub x, x) -> 0
if (N0 == N1)
if (ISD::isBuildVectorAllZeros(N0.Val))
// Zero vectors might be normalized to a particular vector type to ensure
// they are CSE'd. Return it as it is.
return N0;
return DAG.getConstant(0, N->getValueType(0));
// fold (sub c1, c2) -> c1-c2
if (N0C && N1C)

24
test/CodeGen/X86/vec_zero-2.ll Normal file
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@ -0,0 +1,24 @@
; RUN: llvm-as < %s | llc -march=x86 -mattr=+sse2
define i32 @t() {
entry:
br i1 true, label %bb4743, label %bb1656
bb1656: ; preds = %entry
ret i32 0
bb1664: ; preds = %entry
br i1 false, label %bb5310, label %bb4743
bb4743: ; preds = %bb1664
%tmp5256 = bitcast <2 x i64> zeroinitializer to <8 x i16> ; <<8 x i16>> [#uses=1]
%tmp5257 = sub <8 x i16> %tmp5256, zeroinitializer ; <<8 x i16>> [#uses=1]
%tmp5258 = bitcast <8 x i16> %tmp5257 to <2 x i64> ; <<2 x i64>> [#uses=1]
%tmp5265 = bitcast <2 x i64> %tmp5258 to <8 x i16> ; <<8 x i16>> [#uses=1]
%tmp5266 = call <8 x i16> @llvm.x86.sse2.packuswb.128( <8 x i16> %tmp5265, <8 x i16> zeroinitializer ) nounwind readnone ; <<8 x i16>> [#uses=1]
%tmp5267 = bitcast <8 x i16> %tmp5266 to <2 x i64> ; <<2 x i64>> [#uses=1]
%tmp5294 = and <2 x i64> zeroinitializer, %tmp5267 ; <<2 x i64>> [#uses=1]
br label %bb5310
bb5310: ; preds = %bb4743, %bb1664
%tmp5294.pn = phi <2 x i64> [ %tmp5294, %bb4743 ], [ zeroinitializer, %bb1664 ] ; <<2 x i64>> [#uses=0]
ret i32 0
}
declare <8 x i16> @llvm.x86.sse2.packuswb.128(<8 x i16>, <8 x i16>) nounwind readnone