Automerge: SeparateConstOffsetFromGEP: Avoid looking at constant uses (#134685)

We could be more aggressive and inspect uses of global variables,
if the use context instruction is in the same function.

Author: arsenm

Diff for: llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp

@@ -1353,6 +1353,11 @@ bool SeparateConstOffsetFromGEP::isLegalToSwapOperand(
 }
 
 bool SeparateConstOffsetFromGEP::hasMoreThanOneUseInLoop(Value *V, Loop *L) {
+  // TODO: Could look at uses of globals, but we need to make sure we are
+  // looking at the correct function.
+  if (isa<Constant>(V))
+    return false;
+
   int UsesInLoop = 0;
   for (User *U : V->users()) {
     if (Instruction *User = dyn_cast<Instruction>(U))

Diff for: llvm/test/Transforms/SeparateConstOffsetFromGEP/AMDGPU/lower-gep.ll

@@ -425,8 +425,8 @@ define amdgpu_kernel void @multi_use_in_loop_global_base_address(ptr addrspace(1
 ; CHECK-NEXT:    [[TMP25]] = add nuw nsw i32 [[TMP13]], 1
 ; CHECK-NEXT:    [[TMP0:%.*]] = sext i32 [[TMP13]] to i64
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl i64 [[TMP0]], 2
-; CHECK-NEXT:    [[UGLYGEP:%.*]] = getelementptr i8, ptr addrspace(1) @extern_array_1, i64 [[TMP1]]
-; CHECK-NEXT:    [[UGLYGEP2:%.*]] = getelementptr i8, ptr addrspace(1) [[UGLYGEP]], i64 4
+; CHECK-NEXT:    [[UGLYGEP:%.*]] = getelementptr i8, ptr addrspace(1) @extern_array_1, i64 4
+; CHECK-NEXT:    [[UGLYGEP2:%.*]] = getelementptr i8, ptr addrspace(1) [[UGLYGEP]], i64 [[TMP1]]
 ; CHECK-NEXT:    [[TMP28:%.*]] = load i32, ptr addrspace(1) [[UGLYGEP2]], align 4
 ; CHECK-NEXT:    [[TMP29:%.*]] = add i32 [[TMP24]], [[TMP12]]
 ; CHECK-NEXT:    [[TMP30]] = add i32 [[TMP29]], [[TMP28]]