[clang] Assume a for-in loop is in bounds and cannot overflow (PR #94883)

[via cfe-commits]

https://github.com/AtariDreams updated 
https://github.com/llvm/llvm-project/pull/94883

>From e50a348e54b90212f7061458010cfa181816f363 Mon Sep 17 00:00:00 2001
From: Rose <gfunni...@gmail.com>
Date: Sat, 8 Jun 2024 22:30:53 -0400
Subject: [PATCH] [CodeGen] Assume a for-in loop is in bounds and cannot
 overflow

When accessing data in the buffer, we know we won't overrun the buffer, so we 
know it is inbounds. In addition, we know that the addition to increase the 
index is also NUW because the buffer's end has to be unsigned-greater-than 0, 
which becomes untrue if the bounds ever has an unsigned wrap.
---
 clang/lib/CodeGen/CGObjC.cpp         | 4 ++--
 clang/test/CodeGenObjC/arc-foreach.m | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/clang/lib/CodeGen/CGObjC.cpp b/clang/lib/CodeGen/CGObjC.cpp
index 281b2d9795f6c..80a64d8e4cdd9 100644
--- a/clang/lib/CodeGen/CGObjC.cpp
+++ b/clang/lib/CodeGen/CGObjC.cpp
@@ -1952,7 +1952,7 @@ void CodeGenFunction::EmitObjCForCollectionStmt(const 
ObjCForCollectionStmt &S){
     Builder.CreateLoad(StateItemsPtr, "stateitems");
 
   // Fetch the value at the current index from the buffer.
-  llvm::Value *CurrentItemPtr = Builder.CreateGEP(
+  llvm::Value *CurrentItemPtr = Builder.CreateInBoundsGEP(
       ObjCIdType, EnumStateItems, index, "currentitem.ptr");
   llvm::Value *CurrentItem =
     Builder.CreateAlignedLoad(ObjCIdType, CurrentItemPtr, getPointerAlign());
@@ -2028,7 +2028,7 @@ void CodeGenFunction::EmitObjCForCollectionStmt(const 
ObjCForCollectionStmt &S){
 
   // First we check in the local buffer.
   llvm::Value *indexPlusOne =
-      Builder.CreateAdd(index, llvm::ConstantInt::get(NSUIntegerTy, 1));
+      Builder.CreateNUWAdd(index, llvm::ConstantInt::get(NSUIntegerTy, 1));
 
   // If we haven't overrun the buffer yet, we can continue.
   // Set the branch weights based on the simplifying assumption that this is
diff --git a/clang/test/CodeGenObjC/arc-foreach.m 
b/clang/test/CodeGenObjC/arc-foreach.m
index 71edc5161303c..9f7b60aef7a1b 100644
--- a/clang/test/CodeGenObjC/arc-foreach.m
+++ b/clang/test/CodeGenObjC/arc-foreach.m
@@ -53,7 +53,7 @@ void test0(NSArray *array) {
 
 // CHECK-LP64:      [[T0:%.*]] = getelementptr inbounds [[STATE_T]], ptr 
[[STATE]], i32 0, i32 1
 // CHECK-LP64-NEXT: [[T1:%.*]] = load ptr, ptr [[T0]]
-// CHECK-LP64-NEXT: [[T2:%.*]] = getelementptr ptr, ptr [[T1]], i64
+// CHECK-LP64-NEXT: [[T2:%.*]] = getelementptr inbounds ptr, ptr [[T1]], i64
 // CHECK-LP64-NEXT: [[T3:%.*]] = load ptr, ptr [[T2]]
 // CHECK-LP64-NEXT: store ptr [[T3]], ptr [[X]]
 
@@ -100,7 +100,7 @@ void test1(NSArray *array) {
 
 // CHECK-LP64:      [[T0:%.*]] = getelementptr inbounds [[STATE_T]], ptr 
[[STATE]], i32 0, i32 1
 // CHECK-LP64-NEXT: [[T1:%.*]] = load ptr, ptr [[T0]]
-// CHECK-LP64-NEXT: [[T2:%.*]] = getelementptr ptr, ptr [[T1]], i64
+// CHECK-LP64-NEXT: [[T2:%.*]] = getelementptr inbounds ptr, ptr [[T1]], i64
 // CHECK-LP64-NEXT: [[T3:%.*]] = load ptr, ptr [[T2]]
 // CHECK-LP64-NEXT: call ptr @llvm.objc.initWeak(ptr [[X]], ptr [[T3]])
 

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