[InstCombine][foldPHIArgGEPIntoPHI] Early return for const vector index for gep inst (#138661)

Author: haonanya1

llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp

@@ -574,8 +574,8 @@ Instruction *InstCombinerImpl::foldPHIArgGEPIntoPHI(PHINode &PN) {
       // substantially cheaper to compute for the constants, so making it a
       // variable index could pessimize the path.  This also handles the case
       // for struct indices, which must always be constant.
-      if (isa<ConstantInt>(FirstInst->getOperand(Op)) ||
-          isa<ConstantInt>(GEP->getOperand(Op)))
+      if (isa<Constant>(FirstInst->getOperand(Op)) ||
+          isa<Constant>(GEP->getOperand(Op)))
         return nullptr;
 
       if (FirstInst->getOperand(Op)->getType() !=

llvm/test/Transforms/InstCombine/fold-phi-arg-gep-to-phi-negative.ll

@@ -0,0 +1,39 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+%foo = type { i16, i16, i16 }
+
+define <16 x ptr> @test(i1 %tobool) {
+; CHECK-LABEL: define <16 x ptr> @test(
+; CHECK-SAME: i1 [[TOBOOL:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[LANE_0:%.*]] = alloca [[FOO:%.*]], align 16
+; CHECK-NEXT:    [[LANE_15:%.*]] = insertelement <16 x ptr> poison, ptr [[LANE_0]], i64 0
+; CHECK-NEXT:    br i1 [[TOBOOL]], label %[[F1:.*]], label %[[F0:.*]]
+; CHECK:       [[F0]]:
+; CHECK-NEXT:    [[MM_VECTORGEP:%.*]] = getelementptr inbounds [[FOO]], <16 x ptr> [[LANE_15]], <16 x i64> zeroinitializer, <16 x i32> splat (i32 1)
+; CHECK-NEXT:    br label %[[MERGE:.*]]
+; CHECK:       [[F1]]:
+; CHECK-NEXT:    [[MM_VECTORGEP2:%.*]] = getelementptr inbounds [[FOO]], <16 x ptr> [[LANE_15]], <16 x i64> zeroinitializer, <16 x i32> splat (i32 2)
+; CHECK-NEXT:    br label %[[MERGE]]
+; CHECK:       [[MERGE]]:
+; CHECK-NEXT:    [[VEC_PHI:%.*]] = phi <16 x ptr> [ [[MM_VECTORGEP]], %[[F0]] ], [ [[MM_VECTORGEP2]], %[[F1]] ]
+; CHECK-NEXT:    ret <16 x ptr> [[VEC_PHI]]
+;
+entry:
+  %lane.0 = alloca %foo, align 16
+  %lane.15 = insertelement <16 x ptr> poison, ptr %lane.0, i64 0
+  %mm_vectorGEP = getelementptr inbounds %foo, <16 x ptr> %lane.15, <16 x i64> zeroinitializer, <16 x i32> splat (i32 1)
+  %mm_vectorGEP2 = getelementptr inbounds %foo, <16 x ptr> %lane.15, <16 x i64> zeroinitializer, <16 x i32> splat (i32 2)
+  br i1 %tobool, label %f1, label %f0
+
+f0:
+  br label %merge
+
+f1:
+  br label %merge
+
+merge:
+  %vec.phi = phi <16 x ptr> [ %mm_vectorGEP, %f0], [ %mm_vectorGEP2, %f1 ]
+  ret <16 x ptr> %vec.phi
+}