[PATCH] D18850: [X86]: Fix for PR27251
Kevin B. Smith via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 7 08:35:35 PDT 2016
kbsmith1 updated this revision to Diff 52928.
kbsmith1 added a comment.
Addressed Ahmed's review comments.
http://reviews.llvm.org/D18850
Files:
lib/Target/X86/X86ISelLowering.cpp
test/CodeGen/X86/vector-blend.ll
Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -27262,9 +27262,24 @@
if (V) {
assert(EltBits == 8 || EltBits == 16 || EltBits == 32);
- return DAG.getBitcast(
- VT, DAG.getNode(ISD::SUB, DL, MaskVT,
- DAG.getNode(ISD::XOR, DL, MaskVT, V, Mask), Mask));
+ SDValue SubOp1 = DAG.getNode(ISD::XOR, DL, MaskVT, V, Mask);
+ SDValue SubOp2 = Mask;
+
+ // If the negate was on the false side of the select, then
+ // the operands of the SUB need to be swapped. PR 27251.
+ // This is because the pattern being matched above is
+ // (vselect M, (sub (0, X), X) -> (sub (xor X, M), M)
+ // but if the pattern matched was
+ // (vselect M, X, (sub (0, X))), that is really negation of the pattern
+ // above, -(vselect M, (sub 0, X), X), and therefore the replacement
+ // pattern also needs to be a negation of the replacement pattern above.
+ // And -(sub X, Y) is just sub (Y, X), so swapping the operands of the
+ // sub accomplishes the negation of the replacement pattern.
+ if (V == Y)
+ std::swap(SubOp1, SubOp2);
+
+ return DAG.getBitcast(VT,
+ DAG.getNode(ISD::SUB, DL, MaskVT, SubOp1, SubOp2));
}
}
Index: test/CodeGen/X86/vector-blend.ll
===================================================================
--- test/CodeGen/X86/vector-blend.ll
+++ test/CodeGen/X86/vector-blend.ll
@@ -1010,16 +1010,18 @@
; SSE2-NEXT: pslld $31, %xmm1
; SSE2-NEXT: psrad $31, %xmm1
; SSE2-NEXT: pxor %xmm1, %xmm0
-; SSE2-NEXT: psubd %xmm1, %xmm0
+; SSE2-NEXT: psubd %xmm0, %xmm1
+; SSE2-NEXT: movdqa %xmm1, %xmm0
; SSE2-NEXT: retq
;
; SSSE3-LABEL: blend_neg_logic_v4i32_2:
; SSSE3: # BB#0: # %entry
; SSSE3-NEXT: psrld $31, %xmm1
; SSSE3-NEXT: pslld $31, %xmm1
; SSSE3-NEXT: psrad $31, %xmm1
; SSSE3-NEXT: pxor %xmm1, %xmm0
-; SSSE3-NEXT: psubd %xmm1, %xmm0
+; SSSE3-NEXT: psubd %xmm0, %xmm1
+; SSSE3-NEXT: movdqa %xmm1, %xmm0
; SSSE3-NEXT: retq
;
; SSE41-LABEL: blend_neg_logic_v4i32_2:
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