[PATCH] D137073: [clang] Fix inline builtin functions of an __asm__ renamed function with symbol prefixes

[Martin Storsjö via Phabricator via cfe-commits]

mstorsjo created this revision.
mstorsjo added reviewers: aaron.ballman, rnk.
Herald added a project: All.
mstorsjo requested review of this revision.
Herald added a project: clang.

If a function is renamed with `__asm__`, the name provided is the
exact symbol name, without any extra implicit symbol prefixes.
If the target does use symbol prefixes, the IR level symbol gets
an `\01` prefix to indicate that it's a literal symbol name to be
taken as is.

When a builtin function is specialized by providing an inline
version of it, that inline function is named `<funcname>.inline`.

When the base function has been renamed due to `__asm__`, the inline
function ends up named `<asmname>.inline`. Up to this point,
things did work as expected before.

However, for targets with symbol prefixes, one codepath that produced
the combined name `<asmname>.inline` used the mangled `asmname` with
`\01` prefix, while others didn't. This patch fixes this.

This fixes the combination of asm renamed builtin function, with
inline override of the function, on any target with symbol
prefixes (such as i386 windows and any Darwin target).

Alternatively, instead of reimplementing this piece of logic
here, should it try to call MangleContext::mangleName somehow?


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D137073

Files:
  clang/lib/CodeGen/CGExpr.cpp
  clang/test/CodeGen/inline-builtin-asm-name.c


Index: clang/test/CodeGen/inline-builtin-asm-name.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/inline-builtin-asm-name.c
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -triple i686-windows-gnu -emit-llvm -o - %s -disable-llvm-optzns | FileCheck %s
+
+// CHECK: call i32 @"\01_asm_func_name.inline"
+
+// CHECK: declare dso_local i32 @"\01_asm_func_name"(ptr noundef, i32 noundef, ptr noundef, ptr noundef)
+
+// CHECK: define internal i32 @"\01_asm_func_name.inline"
+
+// CHECK: call i32 @__mingw_vsnprintf
+
+// CHECK: declare dso_local i32 @__mingw_vsnprintf
+
+typedef unsigned int size_t;
+
+int __mingw_vsnprintf(char *_DstBuf, size_t _MaxCount, const char *_Format, __builtin_va_list _ArgList);
+
+// For the real use case, "_asm_func_name" is actually "___mingw_vsnprintf", but it's renamed in the testcase for disambiguation.
+int vsnprintf(char *__stream, size_t __n, const char *__format, __builtin_va_list __local_argv) __asm__("_asm_func_name");
+
+extern __inline__ __attribute__((__always_inline__, __gnu_inline__))
+int vsnprintf(char *__stream, size_t __n, const char *__format, __builtin_va_list __local_argv)
+{
+  return __mingw_vsnprintf(__stream, __n, __format, __local_argv);
+}
+
+void call(const char* fmt, ...) {
+  char buf[200];
+  __builtin_va_list ap;
+  __builtin_va_start(ap, fmt);
+  vsnprintf(buf, sizeof(buf), fmt, ap);
+  __builtin_va_end(ap);
+}
Index: clang/lib/CodeGen/CGExpr.cpp
===================================================================
--- clang/lib/CodeGen/CGExpr.cpp
+++ clang/lib/CodeGen/CGExpr.cpp
@@ -5014,8 +5014,18 @@
     std::string NoBuiltinFD = ("no-builtin-" + FD->getName()).str();
     std::string NoBuiltins = "no-builtins";
 
-    auto *A = FD->getAttr<AsmLabelAttr>();
-    StringRef Ident = A ? A->getLabel() : FD->getName();
+    StringRef Ident = FD->getName();
+
+    std::string AsmName;
+    if (auto *A = FD->getAttr<AsmLabelAttr>()) {
+      StringRef UserLabelPrefix =
+          CGF.getContext().getTargetInfo().getUserLabelPrefix();
+      if (!UserLabelPrefix.empty())
+        AsmName += '\01'; // LLVM IR Marker for __asm("foo")
+      AsmName += A->getLabel();
+      Ident = AsmName;
+    }
+
     std::string FDInlineName = (Ident + ".inline").str();
 
     bool IsPredefinedLibFunction =


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