From bcbfc03bd6355523e8d82c2b77b1e451a3d48a19 Mon Sep 17 00:00:00 2001
From: Yury Gribov <tetra2005@gmail.com>
Date: Thu, 21 Dec 2023 17:44:11 +0300
Subject: [PATCH] [CIR][CodeGen] Use signed type for result of ptrdiff
 operation. (#355)

Before this fix attached test case has been failing due to type mismatch
(signed vs unsigned).
---
 clang/lib/CIR/CodeGen/CIRGenModule.cpp  |  4 ++++
 clang/lib/CIR/CodeGen/CIRGenTypeCache.h |  3 ++-
 clang/test/CIR/CodeGen/ptr_diff.cpp     | 15 +++++++++++++--
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/clang/lib/CIR/CodeGen/CIRGenModule.cpp b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
index e7717e57e8b4..a2b2e2277a9b 100644
--- a/clang/lib/CIR/CodeGen/CIRGenModule.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
@@ -162,6 +162,10 @@ CIRGenModule::CIRGenModule(mlir::MLIRContext &context,
   // TODO: ConstGlobalsPtrTy
   // TODO: ASTAllocaAddressSpace
 
+  PtrDiffTy = ::mlir::cir::IntType::get(
+      builder.getContext(), astCtx.getTargetInfo().getMaxPointerWidth(),
+      /*isSigned=*/true);
+
   mlir::cir::sob::SignedOverflowBehavior sob;
   switch (langOpts.getSignedOverflowBehavior()) {
   case clang::LangOptions::SignedOverflowBehaviorTy::SOB_Defined:
diff --git a/clang/lib/CIR/CodeGen/CIRGenTypeCache.h b/clang/lib/CIR/CodeGen/CIRGenTypeCache.h
index cea3f07922e0..ac3442626ca8 100644
--- a/clang/lib/CIR/CodeGen/CIRGenTypeCache.h
+++ b/clang/lib/CIR/CodeGen/CIRGenTypeCache.h
@@ -49,9 +49,10 @@ struct CIRGenTypeCache {
   union {
     mlir::Type UIntPtrTy;
     mlir::Type SizeTy;
-    mlir::Type PtrDiffTy;
   };
 
+  mlir::Type PtrDiffTy;
+
   /// void* in address space 0
   mlir::cir::PointerType VoidPtrTy;
   mlir::cir::PointerType UInt8PtrTy;
diff --git a/clang/test/CIR/CodeGen/ptr_diff.cpp b/clang/test/CIR/CodeGen/ptr_diff.cpp
index 924162d3c790..ebaa5ec6bfac 100644
--- a/clang/test/CIR/CodeGen/ptr_diff.cpp
+++ b/clang/test/CIR/CodeGen/ptr_diff.cpp
@@ -9,5 +9,16 @@ size_type size(unsigned long *_start, unsigned long *_finish) {
 // CHECK: cir.func @_Z4sizePmS_(%arg0: !cir.ptr<!u64i>
 // CHECK:   %3 = cir.load %1 : cir.ptr <!cir.ptr<!u64i>>, !cir.ptr<!u64i>
 // CHECK:   %4 = cir.load %0 : cir.ptr <!cir.ptr<!u64i>>, !cir.ptr<!u64i>
-// CHECK:   %5 = cir.ptr_diff(%3, %4) : !cir.ptr<!u64i> -> !u64i
-  
\ No newline at end of file
+// CHECK:   %5 = cir.ptr_diff(%3, %4) : !cir.ptr<!u64i> -> !s64i
+// CHECK:   %6 = cir.cast(integral, %5 : !s64i), !u64i
+
+long add(char *a, char *b) {
+  return a - b + 1;
+}
+
+// CHECK: cir.func @_Z3addPcS_(%arg0: !cir.ptr<!s8i>
+//          %5 = cir.ptr_diff(%3, %4) : !cir.ptr<!s8i> -> !s64i
+//          %6 = cir.const(#cir.int<1> : !s32i) : !s32i
+//          %7 = cir.cast(integral, %6 : !s32i), !s64i
+//          %8 = cir.binop(add, %5, %7) : !s64i
+