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[DAGCombine] Don't fold a trunc if it feeds an anyext

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Legalization tends to create anyext(trunc) patterns. This should always be
combined - into either a single trunc, a single ext, or nothing if the
types match exactly. But if we happen to combine the trunc first, we may pull
the trunc away from the anyext or make it implicit (e.g. the truncate(extract)
-> extract(bitcast) fold).

To prevent this, we can avoid doing the fold, similarly to how we already handle
fpround(fpextend).

Differential Revision: https://reviews.llvm.org/D23893


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280386 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Kuperstein 2016-09-01 17:59:24 +00:00
parent 97a9f60dce
commit 1b35037238
3 changed files with 8 additions and 8 deletions
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4
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -7135,6 +7135,10 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
return N0.getOperand(0);
}
// If this is anyext(trunc), don't fold it, allow ourselves to be folded.
if (N->hasOneUse() && (N->use_begin()->getOpcode() == ISD::ANY_EXTEND))
return SDValue();
// Fold extract-and-trunc into a narrow extract. For example:
// i64 x = EXTRACT_VECTOR_ELT(v2i64 val, i32 1)
// i32 y = TRUNCATE(i64 x)

5
test/CodeGen/X86/2011-10-21-widen-cmp.ll
View File

@ -10,10 +10,7 @@ define void @cmp_2_floats() {
; CHECK-NEXT: cmpordps %xmm0, %xmm0
; CHECK-NEXT: pmovzxdq {{.*#+}} xmm0 = xmm0[0],zero,xmm0[1],zero
; CHECK-NEXT: psllq $32, %xmm0
; CHECK-NEXT: pshufd {{.*#+}} xmm1 = xmm0[1,1,3,3]
; CHECK-NEXT: psrad $31, %xmm0
; CHECK-NEXT: pblendw {{.*#+}} xmm0 = xmm1[0,1],xmm0[2,3],xmm1[4,5],xmm0[6,7]
; CHECK-NEXT: pshufd {{.*#+}} xmm0 = xmm0[0,2,2,3]
; CHECK-NEXT: pshufd {{.*#+}} xmm0 = xmm0[1,3,2,3]
; CHECK-NEXT: pslld $31, %xmm0
; CHECK-NEXT: blendvps %xmm0, %xmm0
; CHECK-NEXT: movlps %xmm0, (%rax)

7
test/CodeGen/X86/mem-intrin-base-reg.ll
View File

@ -8,15 +8,12 @@ target triple = "i686-pc-windows-msvc"
; for when this is necessary. Typically, we chose ESI for the base register,
; which all of the X86 string instructions use.
; The pattern of vector icmp and extractelement is used in these tests because
; it forces creation of an aligned stack temporary. Perhaps such temporaries
; shouldn't be aligned.
declare void @escape_vla_and_icmp(i8*, i1 zeroext)
declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture readonly, i32, i32, i1)
declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1)
define i32 @memcpy_novla_vector(<4 x i32>* %vp0, i8* %a, i8* %b, i32 %n, i1 zeroext %cond) {
%foo = alloca <4 x i32>, align 16
call void @llvm.memcpy.p0i8.p0i8.i32(i8* %a, i8* %b, i32 128, i32 4, i1 false)
br i1 %cond, label %spill_vectors, label %no_vectors
@ -42,6 +39,7 @@ spill_vectors:
; CHECK: rep;movsl
define i32 @memcpy_vla_vector(<4 x i32>* %vp0, i8* %a, i8* %b, i32 %n, i1 zeroext %cond) {
%foo = alloca <4 x i32>, align 16
call void @llvm.memcpy.p0i8.p0i8.i32(i8* %a, i8* %b, i32 128, i32 4, i1 false)
br i1 %cond, label %spill_vectors, label %no_vectors
@ -70,6 +68,7 @@ spill_vectors:
; stosd doesn't clobber esi, so we can use it.
define i32 @memset_vla_vector(<4 x i32>* %vp0, i8* %a, i32 %n, i1 zeroext %cond) {
%foo = alloca <4 x i32>, align 16
call void @llvm.memset.p0i8.i32(i8* %a, i8 42, i32 128, i32 4, i1 false)
br i1 %cond, label %spill_vectors, label %no_vectors