[llvm] [InstSimplify] Add additional checks when substituting pointers (PR #125385)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-analysis

Author: Yingwei Zheng (dtcxzyw)

<details>
<summary>Changes</summary>

Compile-time impact: https://llvm-compile-time-tracker.com/compare.php?from=d09b521624f263b5f1296f8d4771836b97e600cb&to=e437ba2cb83bb965e13ef00727671896f03ff84f&stat=instructions:u
IR diff looks acceptable.
Closes https://github.com/llvm/llvm-project/issues/115574


---
Full diff: https://github.com/llvm/llvm-project/pull/125385.diff


2 Files Affected:

- (modified) llvm/lib/Analysis/InstructionSimplify.cpp (+11-6) 
- (modified) llvm/test/Transforms/InstSimplify/select-icmp.ll (+20) 


``````````diff
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 21c937530cd869..3cbc4107433ef3 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"
@@ -4731,12 +4732,16 @@ 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 a6ef937760a589..9895271b35ac7f 100755
--- a/llvm/test/Transforms/InstSimplify/select-icmp.ll
+++ b/llvm/test/Transforms/InstSimplify/select-icmp.ll
@@ -244,3 +244,23 @@ 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
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/125385