[InstCombine] add more insert-extract tests for D52439; NFC

rotateright · rotateright · commit 22ae8dabb547 · 2018-10-01T14:29:09.000Z
The first attempt at this transform:
rL343407
...was reverted:
rL343458
...because it did not handle the case where we bitcast to FP. 
The patch was already limited to avoid the case where we
bitcast from FP, but we might want to transform that too.

llvm-svn: 343480
diff --git a/llvm/test/Transforms/InstCombine/extractelement.ll b/llvm/test/Transforms/InstCombine/extractelement.ll
@@ -139,3 +139,29 @@ define i8 @bitcasted_inselt_wide_source_uses(i32 %x) {
   ret i8 %r
 }
 
+define float @bitcasted_inselt_to_FP(i64 %x) {
+; ANY-LABEL: @bitcasted_inselt_to_FP(
+; ANY-NEXT:    [[I:%.*]] = insertelement <2 x i64> undef, i64 [[X:%.*]], i32 0
+; ANY-NEXT:    [[B:%.*]] = bitcast <2 x i64> [[I]] to <4 x float>
+; ANY-NEXT:    [[R:%.*]] = extractelement <4 x float> [[B]], i32 1
+; ANY-NEXT:    ret float [[R]]
+;
+  %i = insertelement <2 x i64> undef, i64 %x, i32 0
+  %b = bitcast <2 x i64> %i to <4 x float>
+  %r = extractelement <4 x float> %b, i32 1
+  ret float %r
+}
+
+define i32 @bitcasted_inselt_from_FP(double %x) {
+; ANY-LABEL: @bitcasted_inselt_from_FP(
+; ANY-NEXT:    [[I:%.*]] = insertelement <2 x double> undef, double [[X:%.*]], i32 0
+; ANY-NEXT:    [[B:%.*]] = bitcast <2 x double> [[I]] to <4 x i32>
+; ANY-NEXT:    [[R:%.*]] = extractelement <4 x i32> [[B]], i32 1
+; ANY-NEXT:    ret i32 [[R]]
+;
+  %i = insertelement <2 x double> undef, double %x, i32 0
+  %b = bitcast <2 x double> %i to <4 x i32>
+  %r = extractelement <4 x i32> %b, i32 1
+  ret i32 %r
+}
+
