[llvm] [GlobalISel] Fix store merging incorrectly classifying an unknown index expr as 0. (PR #90375)

[Thorsten Schütt via llvm-commits]

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@@ -826,3 +828,43 @@ body:             |
     RET_ReallyLR
 
 ...
+---
+name:            invalid_zero_offset_no_merge
+alignment:       4
+tracksRegLiveness: true
+liveins:
+  - { reg: '$x0' }
+frameInfo:
+  maxAlignment:    1
+machineFunctionInfo: {}
+body:             |
+  bb.1 (%ir-block.1):
+    liveins: $x0
+
+    ; CHECK-LABEL: name: invalid_zero_offset_no_merge
+    ; CHECK: liveins: $x0
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s64) = COPY $x0
+    ; CHECK-NEXT: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 2
+    ; CHECK-NEXT: [[SHL:%[0-9]+]]:_(s64) = G_SHL [[COPY]], [[C]](s64)
+    ; CHECK-NEXT: [[GV:%[0-9]+]]:_(p0) = G_GLOBAL_VALUE @G
+    ; CHECK-NEXT: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[GV]], [[SHL]](s64)
+    ; CHECK-NEXT: [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
+    ; CHECK-NEXT: G_STORE [[C1]](s32), [[PTR_ADD]](p0) :: (store (s32) into %ir.2)
+    ; CHECK-NEXT: [[C2:%[0-9]+]]:_(s64) = G_CONSTANT i64 4
+    ; CHECK-NEXT: [[PTR_ADD1:%[0-9]+]]:_(p0) = nuw G_PTR_ADD [[GV]], [[C2]](s64)
+    ; CHECK-NEXT: G_STORE [[C1]](s32), [[PTR_ADD1]](p0) :: (store (s32) into `ptr getelementptr inbounds ([10 x i32], ptr @G, i64 0, i64 1)`)
+    ; CHECK-NEXT: RET_ReallyLR
+    %0:_(s64) = COPY $x0
+    %9:_(s64) = G_CONSTANT i64 2
+    %3:_(s64) = G_SHL %0, %9(s64)
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tschuett wrote:

It is similar to the reported issue, but G_MUL vs. G_SHL?!?

https://github.com/llvm/llvm-project/pull/90375