[mips][msa] Float vector constants cannot use ldi.[wd] directly. Bitcast from the appropriate integer vector type.

Fixes an instruction selection failure detected by llvm-stress.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195444 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Mips/MipsSEISelLowering.cpp

@@ -2210,7 +2210,9 @@ SDValue MipsSETargetLowering::lowerBUILD_VECTOR(SDValue Op,
       return SDValue();
 
     // If the value fits into a simm10 then we can use ldi.[bhwd]
-    if (SplatValue.isSignedIntN(10))
+    // However, if it isn't an integer type we will have to bitcast from an
+    // integer type first.
+    if (ResTy.isInteger() && SplatValue.isSignedIntN(10))
       return Op;
 
     EVT ViaVecTy;

test/CodeGen/Mips/msa/llvm-stress-s2501752154-simplified.ll

@@ -0,0 +1,27 @@
+; 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 originally failed for MSA with a "Cannot select ..." error.
+; This happened because the legalizer treated undef's in the <4 x float>
+; constant as equivalent to the defined elements when checking if it a constant
+; splat, but then proceeded to legalize the undef's to zero, leaving it as a
+; non-splat that cannot be selected. It should have eliminated the undef's by
+; rewriting the splat constant.
+
+; It should at least successfully build.
+
+define void @autogen_SD2501752154() {
+BB:
+  %BC = bitcast <4 x i32> <i32 -1, i32 -1, i32 undef, i32 undef> to <4 x float>
+  br label %CF74
+
+CF74:                                             ; preds = %CF74, %CF
+  %E54 = extractelement <1 x i1> undef, i32 0
+  br i1 %E54, label %CF74, label %CF79
+
+CF79:                                             ; preds = %CF75
+  %I63 = insertelement <4 x float> %BC, float undef, i32 0
+  ret void
+}