[test][InstCombine] Add a test case for constant folding for uniformly initialized array

[khei4]

Summary

To enable ConstantFolding to handle load/GEP instruction for uniformly initialized aggregate types. This patch only contains tests. Implementation patches coming later.
Goal proof: https://alive2.llvm.org/ce/z/oZtVby
motivated by https://github.com/rust-lang/rust/issues/107208
(this is my first patch and I don't have commit access )

[khei4]

Similar test cases exist already. Abandon this revision.

llvm/test/Transforms/InstCombine/load.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -passes=instcombine -S < %s | FileCheck %s
 
 target datalayout = "e-m:e-p:64:64:64-i64:64-f80:128-n8:16:32:64-S128-ni:1"
 
 @X = constant i32 42    ; <ptr> [#uses=2]
 @X2 = constant i32 47   ; <ptr> [#uses=1]
 @Y = constant [2 x { i32, float }] [ { i32, float } { i32 12, float 1.000000e+00 }, { i32, float } { i32 37, float 0x3FF3B2FEC0000000 } ]    ; <ptr> [#uses=2]
 @Z = constant [2 x { i32, float }] zeroinitializer    ; <ptr> [#uses=1]
 
 @GLOBAL = internal constant [4 x i32] zeroinitializer
+@GLOBAL1 = internal constant [4 x i32] [i32 1,i32 1,i32 1,i32 1]
 
 
 define i32 @test1() {
 ; CHECK-LABEL: @test1(
 ; CHECK-NEXT:    ret i32 42
 ;
   %B = load i32, ptr @X   ; <i32> [#uses=1]
   ret i32 %B

 ; CHECK-NEXT:    store i32 poison, ptr null, align 4294967296
 ; CHECK-NEXT:    ret i32 poison
 ;
   %V = getelementptr i32, ptr null, i64 %X
   %R = load i32, ptr %V
   ret i32 %R
 }
 
+; TODO: constant fold for global constant uniform array
+define i32 @load_gep_const_uniform_zero_array(i64 %X) {
+; CHECK-LABEL: @load_gep_const_uniform_zero_array(
+; CHECK-NEXT:    [[V:%.*]] = getelementptr inbounds [4 x i32], ptr @GLOBAL, i64 0, i64 [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = load i32, ptr [[V]], align 4
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %V = getelementptr inbounds [4 x i32], ptr @GLOBAL, i64 0, i64 %X
+  %R = load i32, ptr %V
+  ret i32 %R
+}
+
+define i32 @load_gep_const_uniform_array(i64 %X) {
+; CHECK-LABEL: @load_gep_const_uniform_array(
+; CHECK-NEXT:    [[V:%.*]] = getelementptr inbounds [4 x i32], ptr @GLOBAL1, i64 0, i64 [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = load i32, ptr [[V]], align 4
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %V = getelementptr inbounds [4 x i32], ptr @GLOBAL1, i64 0, i64 %X
+  %R = load i32, ptr %V
+  ret i32 %R
+}
+
 define i32 @test7_no_null_opt(i32 %X) #0 {
 ; CHECK-LABEL: @test7_no_null_opt(
 ; CHECK-NEXT:    [[TMP1:%.*]] = sext i32 [[X:%.*]] to i64
 ; CHECK-NEXT:    [[V:%.*]] = getelementptr i32, ptr null, i64 [[TMP1]]
 ; CHECK-NEXT:    [[R:%.*]] = load i32, ptr [[V]], align 4
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %V = getelementptr i32, ptr null, i32 %X               ; <ptr> [#uses=1]