[mips][msa] Fix a corner case in performORCombine() when combining nodes into VSELECT.

Mask == ~InvMask asserts if the width of Mask and InvMask differ.
The combine isn't valid (with two exceptions, see below) if the widths differ
so test for this before testing Mask == ~InvMask.

In the specific cases of Mask=~0 and InvMask=0, as well as Mask=0 and
InvMask=~0, the combine is still valid. However, there are more appropriate
combines that could be used in these cases such as folding x & 0 to 0, or
x & ~0 to x.

llvm-svn: 195364

2 files changed, 41 insertions, 4 deletions

diff --git a/llvm/lib/Target/Mips/MipsSEISelLowering.cpp b/llvm/lib/Target/Mips/MipsSEISelLowering.cpp
index 274cdc1f89a..27d7515c40c 100644
--- a/llvm/lib/Target/Mips/MipsSEISelLowering.cpp
+++ b/llvm/lib/Target/Mips/MipsSEISelLowering.cpp
@@ -594,9 +594,11 @@ static SDValue performORCombine(SDNode *N, SelectionDAG &DAG,
       Cond = Op0Op0;
       IfSet = Op0Op1;
 
-      if (isVSplat(Op1Op0, InvMask, IsLittleEndian) && Mask == ~InvMask)
+      if (isVSplat(Op1Op0, InvMask, IsLittleEndian) &&
+          Mask.getBitWidth() == InvMask.getBitWidth() && Mask == ~InvMask)
         IfClr = Op1Op1;
-      else if (isVSplat(Op1Op1, InvMask, IsLittleEndian) && Mask == ~InvMask)
+      else if (isVSplat(Op1Op1, InvMask, IsLittleEndian) &&
+               Mask.getBitWidth() == InvMask.getBitWidth() && Mask == ~InvMask)
         IfClr = Op1Op0;
 
       IsConstantMask = true;
@@ -609,9 +611,11 @@ static SDValue performORCombine(SDNode *N, SelectionDAG &DAG,
       Cond = Op0Op1;
       IfSet = Op0Op0;
 
-      if (isVSplat(Op1Op0, InvMask, IsLittleEndian) && Mask == ~InvMask)
+      if (isVSplat(Op1Op0, InvMask, IsLittleEndian) &&
+          Mask.getBitWidth() == InvMask.getBitWidth() && Mask == ~InvMask)
         IfClr = Op1Op1;
-      else if (isVSplat(Op1Op1, InvMask, IsLittleEndian) && Mask == ~InvMask)
+      else if (isVSplat(Op1Op1, InvMask, IsLittleEndian) &&
+               Mask.getBitWidth() == InvMask.getBitWidth() && Mask == ~InvMask)
         IfClr = Op1Op0;
 
       IsConstantMask = true;
diff --git a/llvm/test/CodeGen/Mips/msa/llvm-stress-s449609655-simplified.ll b/llvm/test/CodeGen/Mips/msa/llvm-stress-s449609655-simplified.ll
new file mode 100644
index 00000000000..24e27cbf14b
--- /dev/null
+++ b/llvm/test/CodeGen/Mips/msa/llvm-stress-s449609655-simplified.ll
@@ -0,0 +1,33 @@
+; RUN: llc -march=mips < %s
+; RUN: llc -march=mips -mattr=+msa,+fp64 < %s
+; RUN: llc -march=mipsel < %s
+; RUN: llc -march=mipsel -mattr=+msa,+fp64 < %s
+
+; This test is based on an llvm-stress generated test case with seed=449609655
+
+; This test originally failed for MSA with a
+; "Comparison requires equal bit widths" assertion.
+; The legalizer legalized ; the <4 x i8>'s into <4 x i32>'s, then a call to
+; isVSplat() returned the splat value for <i8 -1, i8 -1, ...> as a 32-bit APInt
+; (255), but the zeroinitializer splat value as an 8-bit APInt (0). The
+; assertion occured when trying to check the values were bitwise inverses of
+; each-other.
+;
+; It should at least successfully build.
+
+define void @autogen_SD449609655(i8) {
+BB:
+  %Cmp = icmp ult i8 -3, %0
+  br label %CF78
+
+CF78:                                             ; preds = %CF81, %CF78, %BB
+  %Sl31 = select i1 %Cmp, <4 x i8> <i8 -1, i8 -1, i8 -1, i8 -1>, <4 x i8> zeroinitializer
+  br i1 undef, label %CF78, label %CF81
+
+CF81:                                             ; preds = %CF78
+  br i1 undef, label %CF78, label %CF80
+
+CF80:                                             ; preds = %CF81
+  %I59 = insertelement <4 x i8> %Sl31, i8 undef, i32 1
+  ret void
+}