[InstCombine] Add pre-commit tests. NFC.

Author: dtcxzyw

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -2910,6 +2910,11 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
                           SQ.getWithInstruction(&GEP)))
     return replaceInstUsesWith(GEP, V);
 
+  // // getelementptr inbounds null, idx -> null
+  // if (auto *BaseC = dyn_cast<Constant>(PtrOp))
+  //   if (GEP.isInBounds() && BaseC->isNullValue() && !NullPointerIsDefined(GEP.getFunction(), GEPType->getPointerAddressSpace()))
+  //     return replaceInstUsesWith(GEP, PtrOp);
+
   // For vector geps, use the generic demanded vector support.
   // Skip if GEP return type is scalable. The number of elements is unknown at
   // compile-time.

llvm/test/Transforms/InstCombine/getelementptr.ll

@@ -2019,5 +2019,40 @@ define ptr @gep_merge_nusw_const(ptr %p, i64 %idx, i64 %idx2) {
   ret ptr %gep
 }
 
+define <2 x ptr> @gep_inbounds_null_vec(i64 %idx) {
+; CHECK-LABEL: @gep_inbounds_null_vec(
+; CHECK-NEXT:    [[P:%.*]] = getelementptr inbounds i8, <2 x ptr> zeroinitializer, i64 [[IDX:%.*]]
+; CHECK-NEXT:    ret <2 x ptr> [[P]]
+;
+  %p = getelementptr inbounds i8, <2 x ptr> zeroinitializer, i64 %idx
+  ret <2 x ptr> %p
+}
+
+define <2 x ptr> @gep_inbounds_null_vec_broadcast(<2 x i64> %idx) {
+; CHECK-LABEL: @gep_inbounds_null_vec_broadcast(
+; CHECK-NEXT:    [[P:%.*]] = getelementptr inbounds i8, ptr null, <2 x i64> [[IDX:%.*]]
+; CHECK-NEXT:    ret <2 x ptr> [[P]]
+;
+  %p = getelementptr inbounds i8, ptr null, <2 x i64> %idx
+  ret <2 x ptr> %p
+}
+
+define ptr @gep_noinbounds_null(i64 %idx) {
+; CHECK-LABEL: @gep_noinbounds_null(
+; CHECK-NEXT:    [[P:%.*]] = getelementptr i8, ptr null, i64 [[IDX:%.*]]
+; CHECK-NEXT:    ret ptr [[P]]
+;
+  %p = getelementptr i8, ptr null, i64 %idx
+  ret ptr %p
+}
+
+define ptr @gep_inbounds_null_null_is_valid(i64 %idx) null_pointer_is_valid {
+; CHECK-LABEL: @gep_inbounds_null_null_is_valid(
+; CHECK-NEXT:    [[P:%.*]] = getelementptr inbounds i8, ptr null, i64 [[IDX:%.*]]
+; CHECK-NEXT:    ret ptr [[P]]
+;
+  %p = getelementptr inbounds i8, ptr null, i64 %idx
+  ret ptr %p
+}
 
 !0 = !{!"branch_weights", i32 2, i32 10}

llvm/test/Transforms/InstCombine/sub-gep.ll

@@ -741,7 +741,7 @@ define i64 @nullptrtoint_scalable_c() {
 ; CHECK-NEXT:    ret i64 [[PTR_IDX]]
 ;
 entry:
-  %ptr = getelementptr inbounds <vscale x 4 x i32>, ptr null, i64 8
+  %ptr = getelementptr nusw <vscale x 4 x i32>, ptr null, i64 8
   %ret = ptrtoint ptr %ptr to i64
   ret i64 %ret
 }
@@ -755,7 +755,7 @@ define i64 @nullptrtoint_scalable_x(i64 %x) {
 ; CHECK-NEXT:    ret i64 [[PTR_IDX]]
 ;
 entry:
-  %ptr = getelementptr inbounds <vscale x 4 x i32>, ptr null, i64 %x
+  %ptr = getelementptr nusw <vscale x 4 x i32>, ptr null, i64 %x
   %ret = ptrtoint ptr %ptr to i64
   ret i64 %ret
 }