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

[Yingwei Zheng via llvm-commits]

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

>From d09b521624f263b5f1296f8d4771836b97e600cb Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sun, 2 Feb 2025 14:50:59 +0800
Subject: [PATCH 1/3] [InstSimplify] Add pre-commit tests. NFC.

---
 .../Transforms/InstSimplify/select-icmp.ll     | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/llvm/test/Transforms/InstSimplify/select-icmp.ll b/llvm/test/Transforms/InstSimplify/select-icmp.ll
index a6ef937760a589..9e738b3b211172 100755
--- a/llvm/test/Transforms/InstSimplify/select-icmp.ll
+++ b/llvm/test/Transforms/InstSimplify/select-icmp.ll
@@ -244,3 +244,21 @@ 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:    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
+}

>From e437ba2cb83bb965e13ef00727671896f03ff84f Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sun, 2 Feb 2025 14:52:44 +0800
Subject: [PATCH 2/3] [InstSimplify] Add additional checks when substituting
 pointers

---
 llvm/lib/Analysis/InstructionSimplify.cpp       | 17 +++++++++++------
 .../test/Transforms/InstSimplify/select-icmp.ll |  4 +++-
 2 files changed, 14 insertions(+), 7 deletions(-)

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 9e738b3b211172..9895271b35ac7f 100755
--- a/llvm/test/Transforms/InstSimplify/select-icmp.ll
+++ b/llvm/test/Transforms/InstSimplify/select-icmp.ll
@@ -247,7 +247,9 @@ cond.end:                                         ; preds = %entry, %cond.true
 
 define ptr @icmp_ptr_eq_replace(ptr %a, ptr %b) {
 ; CHECK-LABEL: @icmp_ptr_eq_replace(
-; CHECK-NEXT:    ret ptr [[B:%.*]]
+; 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

>From 0e3837ba62293e31170eee24691f543a7fa4217d Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sun, 2 Feb 2025 17:20:57 +0800
Subject: [PATCH 3/3] [InstSimplify] Add more tests. NFC.

---
 llvm/test/Transforms/InstSimplify/select-icmp.ll | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/llvm/test/Transforms/InstSimplify/select-icmp.ll b/llvm/test/Transforms/InstSimplify/select-icmp.ll
index 9895271b35ac7f..64c0d1d7553feb 100755
--- a/llvm/test/Transforms/InstSimplify/select-icmp.ll
+++ b/llvm/test/Transforms/InstSimplify/select-icmp.ll
@@ -264,3 +264,15 @@ define ptr @icmp_ptr_eq_replace_null(ptr %a) {
   %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
+}