[PATCH] D47156: [DAGCombiner] isAllOnesConstantOrAllOnesSplatConstant(): look through bitcasts

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: RKSimon, spatel, craig.topper.

As pointed out in https://reviews.llvm.org/D46528, we errneously transform cases like `xor X, -1`,
even though we use said function.
It's because the `-1` is actually a bitcast there.
So i think we can just look through it in the function.


Repository:
  rL LLVM

https://reviews.llvm.org/D47156

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/X86/unfold-masked-merge-vector-variablemask-const.ll


Index: test/CodeGen/X86/unfold-masked-merge-vector-variablemask-const.ll
===================================================================
--- test/CodeGen/X86/unfold-masked-merge-vector-variablemask-const.ll
+++ test/CodeGen/X86/unfold-masked-merge-vector-variablemask-const.ll
@@ -58,20 +58,18 @@
 ;
 ; CHECK-SSE2-LABEL: in_constant_varx_mone:
 ; CHECK-SSE2:       # %bb.0:
-; CHECK-SSE2-NEXT:    movdqa (%rdx), %xmm0
+; CHECK-SSE2-NEXT:    movdqa (%rdi), %xmm0
 ; CHECK-SSE2-NEXT:    pcmpeqd %xmm1, %xmm1
-; CHECK-SSE2-NEXT:    pxor %xmm0, %xmm1
-; CHECK-SSE2-NEXT:    pand (%rdi), %xmm0
-; CHECK-SSE2-NEXT:    por %xmm1, %xmm0
+; CHECK-SSE2-NEXT:    pandn (%rdx), %xmm0
+; CHECK-SSE2-NEXT:    pxor %xmm1, %xmm0
 ; CHECK-SSE2-NEXT:    retq
 ;
 ; CHECK-XOP-LABEL: in_constant_varx_mone:
 ; CHECK-XOP:       # %bb.0:
-; CHECK-XOP-NEXT:    vmovdqa (%rdx), %xmm0
+; CHECK-XOP-NEXT:    vmovdqa (%rdi), %xmm0
 ; CHECK-XOP-NEXT:    vpcmpeqd %xmm1, %xmm1, %xmm1
-; CHECK-XOP-NEXT:    vpxor %xmm1, %xmm0, %xmm1
-; CHECK-XOP-NEXT:    vpand (%rdi), %xmm0, %xmm0
-; CHECK-XOP-NEXT:    vpor %xmm1, %xmm0, %xmm0
+; CHECK-XOP-NEXT:    vpandn (%rdx), %xmm0, %xmm0
+; CHECK-XOP-NEXT:    vpxor %xmm1, %xmm0, %xmm0
 ; CHECK-XOP-NEXT:    retq
   %x = load <4 x i32>, <4 x i32> *%px, align 16
   %y = load <4 x i32>, <4 x i32> *%py, align 16
@@ -134,22 +132,21 @@
 ;
 ; CHECK-SSE2-LABEL: in_constant_varx_mone_invmask:
 ; CHECK-SSE2:       # %bb.0:
-; CHECK-SSE2-NEXT:    movdqa (%rdx), %xmm1
-; CHECK-SSE2-NEXT:    pcmpeqd %xmm0, %xmm0
-; CHECK-SSE2-NEXT:    pxor %xmm0, %xmm0
+; CHECK-SSE2-NEXT:    movdqa (%rdi), %xmm0
+; CHECK-SSE2-NEXT:    pcmpeqd %xmm1, %xmm1
+; CHECK-SSE2-NEXT:    movdqa (%rdx), %xmm2
+; CHECK-SSE2-NEXT:    pxor %xmm1, %xmm2
+; CHECK-SSE2-NEXT:    pandn %xmm2, %xmm0
 ; CHECK-SSE2-NEXT:    pxor %xmm1, %xmm0
-; CHECK-SSE2-NEXT:    pandn (%rdi), %xmm1
-; CHECK-SSE2-NEXT:    por %xmm1, %xmm0
 ; CHECK-SSE2-NEXT:    retq
 ;
 ; CHECK-XOP-LABEL: in_constant_varx_mone_invmask:
 ; CHECK-XOP:       # %bb.0:
-; CHECK-XOP-NEXT:    vmovdqa (%rdx), %xmm0
+; CHECK-XOP-NEXT:    vmovdqa (%rdi), %xmm0
 ; CHECK-XOP-NEXT:    vpcmpeqd %xmm1, %xmm1, %xmm1
-; CHECK-XOP-NEXT:    vpandn (%rdi), %xmm0, %xmm2
-; CHECK-XOP-NEXT:    vpxor %xmm1, %xmm1, %xmm1
+; CHECK-XOP-NEXT:    vpxor (%rdx), %xmm1, %xmm2
+; CHECK-XOP-NEXT:    vpandn %xmm2, %xmm0, %xmm0
 ; CHECK-XOP-NEXT:    vpxor %xmm1, %xmm0, %xmm0
-; CHECK-XOP-NEXT:    vpor %xmm0, %xmm2, %xmm0
 ; CHECK-XOP-NEXT:    retq
   %x = load <4 x i32>, <4 x i32> *%px, align 16
   %y = load <4 x i32>, <4 x i32> *%py, align 16
Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -913,6 +913,8 @@
 // constant integer of all ones (with no undefs).
 // Do not permit build vector implicit truncation.
 static bool isAllOnesConstantOrAllOnesSplatConstant(SDValue N) {
+  if (N.getOpcode() == ISD::BITCAST)
+    return isAllOnesConstantOrAllOnesSplatConstant(N.getOperand(0));
   unsigned BitWidth = N.getScalarValueSizeInBits();
   if (ConstantSDNode *Splat = isConstOrConstSplat(N))
     return Splat->isAllOnesValue() &&


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