[InstCombine] Call simplifyInsertValueInst()

InstCombine is supposed to be a superset of InstSimplify, but we
were not attempting simplification of insertvalue instructions.
As the test change illustrates, we failed to remove some aggregate
construction patterns because of that.

llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp

@@ -1129,6 +1129,11 @@ Instruction *InstCombinerImpl::foldAggregateConstructionIntoAggregateReuse(
 /// It should be transformed to:
 ///  %0 = insertvalue { i8, i32 } undef, i8 %y, 0
 Instruction *InstCombinerImpl::visitInsertValueInst(InsertValueInst &I) {
+  if (Value *V = simplifyInsertValueInst(
+          I.getAggregateOperand(), I.getInsertedValueOperand(), I.getIndices(),
+          SQ.getWithInstruction(&I)))
+    return replaceInstUsesWith(I, V);
+
   bool IsRedundant = false;
   ArrayRef<unsigned int> FirstIndices = I.getIndices();
 

llvm/test/Transforms/InstCombine/aggregate-reconstruction.ll

@@ -305,13 +305,7 @@ end:
 ; Like test2 but with a poison base.
 define [3 x i32] @poison_base([3 x i32] %srcagg) {
 ; CHECK-LABEL: @poison_base(
-; CHECK-NEXT:    [[I0:%.*]] = extractvalue [3 x i32] [[SRCAGG:%.*]], 0
-; CHECK-NEXT:    [[I1:%.*]] = extractvalue [3 x i32] [[SRCAGG]], 1
-; CHECK-NEXT:    [[I2:%.*]] = extractvalue [3 x i32] [[SRCAGG]], 2
-; CHECK-NEXT:    [[I3:%.*]] = insertvalue [3 x i32] poison, i32 [[I0]], 0
-; CHECK-NEXT:    [[I4:%.*]] = insertvalue [3 x i32] [[I3]], i32 [[I1]], 1
-; CHECK-NEXT:    [[I5:%.*]] = insertvalue [3 x i32] [[I4]], i32 [[I2]], 2
-; CHECK-NEXT:    ret [3 x i32] [[I5]]
+; CHECK-NEXT:    ret [3 x i32] [[SRCAGG:%.*]]
 ;
   %i0 = extractvalue [3 x i32] %srcagg, 0
   %i1 = extractvalue [3 x i32] %srcagg, 1