From 074561a4a22f610d756109170285d8626c4cc3bc Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov@redhat.com>
Date: Tue, 8 Feb 2022 17:14:41 +0100
Subject: [PATCH] [Mem2Reg] Check that load type matches alloca type

Alloca promotion can only deal with cases where the load/store
types match the alloca type (it explicitly does not support
bitcasted load/stores).

With opaque pointers this is no longer enforced through the pointer
type, so add an explicit check.
---
 .../Transforms/Utils/PromoteMemoryToRegister.cpp   |  2 +-
 llvm/test/Transforms/Mem2Reg/opaque-ptr.ll         | 25 ++++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/Transforms/Mem2Reg/opaque-ptr.ll

diff --git a/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp b/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
index 01b433b..8d0d4be 100644
--- a/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
+++ b/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
@@ -68,7 +68,7 @@ bool llvm::isAllocaPromotable(const AllocaInst *AI) {
     if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
       // Note that atomic loads can be transformed; atomic semantics do
       // not have any meaning for a local alloca.
-      if (LI->isVolatile())
+      if (LI->isVolatile() || LI->getType() != AI->getAllocatedType())
         return false;
     } else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
       if (SI->getValueOperand() == AI ||
diff --git a/llvm/test/Transforms/Mem2Reg/opaque-ptr.ll b/llvm/test/Transforms/Mem2Reg/opaque-ptr.ll
new file mode 100644
index 0000000..0eec7b6
--- /dev/null
+++ b/llvm/test/Transforms/Mem2Reg/opaque-ptr.ll
@@ -0,0 +1,25 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -mem2reg -opaque-pointers < %s | FileCheck %s
+
+define i32 @test_same_type() {
+; CHECK-LABEL: @test_same_type(
+; CHECK-NEXT:    ret i32 0
+;
+  %p = alloca i32
+  store i32 0, ptr %p
+  %v = load i32, ptr %p
+  ret i32 %v
+}
+
+define i16 @test_different_type() {
+; CHECK-LABEL: @test_different_type(
+; CHECK-NEXT:    [[P:%.*]] = alloca i32, align 4
+; CHECK-NEXT:    store i32 0, ptr [[P]], align 4
+; CHECK-NEXT:    [[V:%.*]] = load i16, ptr [[P]], align 2
+; CHECK-NEXT:    ret i16 [[V]]
+;
+  %p = alloca i32
+  store i32 0, ptr %p
+  %v = load i16, ptr %p
+  ret i16 %v
+}
-- 
2.7.4