- Fix a x86 vector isel bug: illegal transformation of a vector_shuffle into a
shift.
- Add a readme entry for a missing vector_shuffle optimization that results in
awful codegen.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52740 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/README-SSE.txt b/lib/Target/X86/README-SSE.txt
index ad28248..8714424 100644
--- a/lib/Target/X86/README-SSE.txt
+++ b/lib/Target/X86/README-SSE.txt
@@ -808,3 +808,34 @@
With SSE4, it should be
movdqa .LC0(%rip), %xmm0
pinsrb $6, %edi, %xmm0
+
+//===---------------------------------------------------------------------===//
+
+We should transform a shuffle of two vectors of constants into a single vector
+of constants. Also, insertelement of a constant into a vector of constants
+should also result in a vector of constants. e.g. 2008-06-25-VecISelBug.ll.
+
+We compiled it to something horrible:
+
+ .align 4
+LCPI1_1: ## float
+ .long 1065353216 ## float 1
+ .const
+
+ .align 4
+LCPI1_0: ## <4 x float>
+ .space 4
+ .long 1065353216 ## float 1
+ .space 4
+ .long 1065353216 ## float 1
+ .text
+ .align 4,0x90
+ .globl _t
+_t:
+ xorps %xmm0, %xmm0
+ movhps LCPI1_0, %xmm0
+ movss LCPI1_1, %xmm1
+ movaps %xmm0, %xmm2
+ shufps $2, %xmm1, %xmm2
+ shufps $132, %xmm2, %xmm0
+ movaps %xmm0, 0
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 1671442..bc7a4ae 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -2933,12 +2933,12 @@
SelectionDAG &DAG) {
unsigned NumZeros = 0;
for (unsigned i = 0; i < NumElems; ++i) {
- SDOperand Idx = Mask.getOperand(Low ? i : NumElems-i-1);
+ unsigned Index = Low ? i : NumElems-i-1;
+ SDOperand Idx = Mask.getOperand(Index);
if (Idx.getOpcode() == ISD::UNDEF) {
++NumZeros;
continue;
}
- unsigned Index = cast<ConstantSDNode>(Idx)->getValue();
SDOperand Elt = DAG.getShuffleScalarElt(Op.Val, Index);
if (Elt.Val && isZeroNode(Elt))
++NumZeros;
@@ -6373,8 +6373,7 @@
continue;
}
- unsigned Index = cast<ConstantSDNode>(Idx)->getValue();
- SDOperand Elt = DAG.getShuffleScalarElt(N, Index);
+ SDOperand Elt = DAG.getShuffleScalarElt(N, i);
if (!Elt.Val ||
(Elt.getOpcode() != ISD::UNDEF && !ISD::isNON_EXTLoad(Elt.Val)))
return false;