[llvm-branch-commits] [llvm] release/20.x: [InstSimplify] Add additional checks when substituting pointers (#125385) (PR #125398)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: None (llvmbot)

<details>
<summary>Changes</summary>

Backport 1af627b592dd15bbe58136f902ced46251fc344d

Requested by: @<!-- -->dtcxzyw

---
Full diff: https://github.com/llvm/llvm-project/pull/125398.diff


2 Files Affected:

- (modified) llvm/lib/Analysis/InstructionSimplify.cpp (+11-6) 
- (modified) llvm/test/Transforms/InstSimplify/select-icmp.ll (+32) 


``````````diff
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index d69747e30f884d7..4e550f8fa6a9fd1 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -27,6 +27,7 @@
 #include "llvm/Analysis/CmpInstAnalysis.h"
 #include "llvm/Analysis/ConstantFolding.h"
 #include "llvm/Analysis/InstSimplifyFolder.h"
+#include "llvm/Analysis/Loads.h"
 #include "llvm/Analysis/LoopAnalysisManager.h"
 #include "llvm/Analysis/MemoryBuiltins.h"
 #include "llvm/Analysis/OverflowInstAnalysis.h"
@@ -4737,12 +4738,16 @@ static Value *simplifySelectWithICmpCond(Value *CondVal, Value *TrueVal,
   // the arms of the select. See if substituting this value into the arm and
   // simplifying the result yields the same value as the other arm.
   if (Pred == ICmpInst::ICMP_EQ) {
-    if (Value *V = simplifySelectWithEquivalence({{CmpLHS, CmpRHS}}, TrueVal,
-                                                 FalseVal, Q, MaxRecurse))
-      return V;
-    if (Value *V = simplifySelectWithEquivalence({{CmpRHS, CmpLHS}}, TrueVal,
-                                                 FalseVal, Q, MaxRecurse))
-      return V;
+    if (CmpLHS->getType()->isIntOrIntVectorTy() ||
+        canReplacePointersIfEqual(CmpLHS, CmpRHS, Q.DL))
+      if (Value *V = simplifySelectWithEquivalence({{CmpLHS, CmpRHS}}, TrueVal,
+                                                   FalseVal, Q, MaxRecurse))
+        return V;
+    if (CmpLHS->getType()->isIntOrIntVectorTy() ||
+        canReplacePointersIfEqual(CmpRHS, CmpLHS, Q.DL))
+      if (Value *V = simplifySelectWithEquivalence({{CmpRHS, CmpLHS}}, TrueVal,
+                                                   FalseVal, Q, MaxRecurse))
+        return V;
 
     Value *X;
     Value *Y;
diff --git a/llvm/test/Transforms/InstSimplify/select-icmp.ll b/llvm/test/Transforms/InstSimplify/select-icmp.ll
index a6ef937760a5899..64c0d1d7553feb9 100755
--- a/llvm/test/Transforms/InstSimplify/select-icmp.ll
+++ b/llvm/test/Transforms/InstSimplify/select-icmp.ll
@@ -244,3 +244,35 @@ cond.true:                                        ; preds = %entry
 cond.end:                                         ; preds = %entry, %cond.true
   ret i8 0
 }
+
+define ptr @icmp_ptr_eq_replace(ptr %a, ptr %b) {
+; CHECK-LABEL: @icmp_ptr_eq_replace(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq ptr [[A:%.*]], [[B1:%.*]]
+; CHECK-NEXT:    [[B:%.*]] = select i1 [[CMP]], ptr [[A]], ptr [[B1]]
+; CHECK-NEXT:    ret ptr [[B]]
+;
+  %cmp = icmp eq ptr %a, %b
+  %sel = select i1 %cmp, ptr %a, ptr %b
+  ret ptr %sel
+}
+
+define ptr @icmp_ptr_eq_replace_null(ptr %a) {
+; CHECK-LABEL: @icmp_ptr_eq_replace_null(
+; CHECK-NEXT:    ret ptr [[A:%.*]]
+;
+  %cmp = icmp eq ptr %a, null
+  %sel = select i1 %cmp, ptr null, ptr %a
+  ret ptr %sel
+}
+
+define ptr @ptr_eq_replace_same_underlying_object(ptr %st, i64 %i, i64 %j) {
+; CHECK-LABEL: @ptr_eq_replace_same_underlying_object(
+; CHECK-NEXT:    [[B:%.*]] = getelementptr inbounds i8, ptr [[ST:%.*]], i64 [[J:%.*]]
+; CHECK-NEXT:    ret ptr [[B]]
+;
+  %a = getelementptr inbounds i8, ptr %st, i64 %i
+  %b = getelementptr inbounds i8, ptr %st, i64 %j
+  %cmp = icmp eq ptr %a, %b
+  %sel = select i1 %cmp, ptr %a, ptr %b
+  ret ptr %sel
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/125398