[clang][bytecode] Fix __builtin_strchr with unsigned chars

[tbaederr]

Get the zero-extended truncated desired value in that case. Add one RUN line to the constexpr-string.cpp test case, to not increase the runtime of that test too much.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

Changes

Get the zero-extended truncated desired value in that case. Add one RUN line to the constexpr-string.cpp test case, to not increase the runtime of that test too much.

---

Full diff: https://github.com/llvm/llvm-project/pull/164410.diff

2 Files Affected:

• (modified) clang/lib/AST/ByteCode/InterpBuiltin.cpp (+8-2)
• (modified) clang/test/SemaCXX/constexpr-string.cpp (+2)

diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index 39b991c68f0db..7b7e5e866243d 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -2041,10 +2041,16 @@ static bool interp__builtin_memchr(InterpState &S, CodePtr OpPC,
   }
 
   if (ID == Builtin::BIstrchr || ID == Builtin::BI__builtin_strchr) {
+    int64_t DesiredTrunc;
+    if (S.getASTContext().CharTy->isSignedIntegerType())
+      DesiredTrunc =
+          Desired.trunc(S.getASTContext().getCharWidth()).getSExtValue();
+    else
+      DesiredTrunc =
+          Desired.trunc(S.getASTContext().getCharWidth()).getZExtValue();
     // strchr compares directly to the passed integer, and therefore
     // always fails if given an int that is not a char.
-    if (Desired !=
-        Desired.trunc(S.getASTContext().getCharWidth()).getSExtValue()) {
+    if (Desired != DesiredTrunc) {
       S.Stk.push<Pointer>();
       return true;
     }
diff --git a/clang/test/SemaCXX/constexpr-string.cpp b/clang/test/SemaCXX/constexpr-string.cpp
index c456740ef7551..93e234685d284 100644
--- a/clang/test/SemaCXX/constexpr-string.cpp
+++ b/clang/test/SemaCXX/constexpr-string.cpp
@@ -7,6 +7,8 @@
 // RUN: %clang_cc1 %s -triple armebv7-unknown-linux -std=c++2a -fsyntax-only -verify -pedantic -Wno-vla-extension -fno-signed-char
 // RUN: %clang_cc1 %s -triple armebv7-unknown-linux -std=c++2a -fsyntax-only -verify -pedantic -Wno-vla-extension -fno-wchar -DNO_PREDEFINED_WCHAR_T
 
+// RUN: %clang_cc1 %s -triple armebv7-unknown-linux -std=c++2a -fsyntax-only -verify -pedantic -Wno-vla-extension -fno-signed-char -fexperimental-new-constant-interpreter
+
 # 9 "/usr/include/string.h" 1 3 4  // expected-warning {{this style of line directive is a GNU extension}}
 extern "C" {
   typedef decltype(sizeof(int)) size_t;