[llvm] [ValueTracking] Handle idx widths > 64 bit in GetPointerBaseWithConst. (PR #221692)

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llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-analysis

Author: Florian Hahn (fhahn)

<details>
<summary>Changes</summary>

GetPointerBaseWithConstantOffset may be called for GEPs with indices that do not fit into 64 bit. Use trySExtValue to avoid assertions in the newly added tests.

---
Full diff: https://github.com/llvm/llvm-project/pull/221692.diff


2 Files Affected:

- (modified) llvm/include/llvm/Analysis/ValueTracking.h (+8-1) 
- (added) llvm/test/Transforms/DeadStoreElimination/wide-pointer-index-offset.ll (+34) 


``````````diff
diff --git a/llvm/include/llvm/Analysis/ValueTracking.h b/llvm/include/llvm/Analysis/ValueTracking.h
index 87dc4e713929c..9a1fdd0ca05a9 100644
--- a/llvm/include/llvm/Analysis/ValueTracking.h
+++ b/llvm/include/llvm/Analysis/ValueTracking.h
@@ -25,6 +25,7 @@
 #include "llvm/Support/Compiler.h"
 #include <cassert>
 #include <cstdint>
+#include <optional>
 
 namespace llvm {
 
@@ -376,7 +377,13 @@ inline Value *GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset,
   Value *Base =
       Ptr->stripAndAccumulateConstantOffsets(DL, OffsetAPInt, AllowNonInbounds);
 
-  Offset = OffsetAPInt.getSExtValue();
+  std::optional<int64_t> OffsetInt64 = OffsetAPInt.trySExtValue();
+  if (!OffsetInt64) {
+    Offset = 0;
+    return Ptr;
+  }
+
+  Offset = *OffsetInt64;
   return Base;
 }
 inline const Value *
diff --git a/llvm/test/Transforms/DeadStoreElimination/wide-pointer-index-offset.ll b/llvm/test/Transforms/DeadStoreElimination/wide-pointer-index-offset.ll
new file mode 100644
index 0000000000000..12b9e4f148749
--- /dev/null
+++ b/llvm/test/Transforms/DeadStoreElimination/wide-pointer-index-offset.ll
@@ -0,0 +1,34 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
+; RUN: opt -passes=dse -S %s | FileCheck %s
+
+target datalayout = "e-m:e-p:128:128:128"
+
+; Tests with constant offsets that does not fit into i64.
+
+define void @wide_offset_store_not_eliminated(ptr %A) {
+; CHECK-LABEL: define void @wide_offset_store_not_eliminated(
+; CHECK-SAME: ptr [[A:%.*]]) {
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr i8, ptr [[A]], i128 147573952589676412928
+; CHECK-NEXT:    store i32 1, ptr [[GEP]], align 4
+; CHECK-NEXT:    store i32 2, ptr [[A]], align 4
+; CHECK-NEXT:    ret void
+;
+  %gep = getelementptr i8, ptr %A, i128 147573952589676412928
+  store i32 1, ptr %gep, align 4
+  store i32 2, ptr %A, align 4
+  ret void
+}
+
+define void @wide_offset_load_store(ptr %A) {
+; CHECK-LABEL: define void @wide_offset_load_store(
+; CHECK-SAME: ptr [[A:%.*]]) {
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr i8, ptr [[A]], i128 147573952589676412928
+; CHECK-NEXT:    [[L:%.*]] = load i32, ptr [[GEP]], align 4
+; CHECK-NEXT:    store i32 [[L]], ptr [[A]], align 4
+; CHECK-NEXT:    ret void
+;
+  %gep = getelementptr i8, ptr %A, i128 147573952589676412928
+  %l = load i32, ptr %gep, align 4
+  store i32 %l, ptr %A, align 4
+  ret void
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/221692