[PATCH] D82862: [ThinLTO] Always parse module level inline asm with At&t dialect

Hans Wennborg via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Tue Jun 30 04:18:58 PDT 2020


hans created this revision.
hans added a reviewer: pcc.
Herald added subscribers: llvm-commits, dexonsmith, steven_wu, hiraditya, inglorion.
Herald added a project: LLVM.

clang-cl passes -x86-asm-syntax=intel to the cc1 invocation so that assembly listings produced by the /FA flag are printed in intel dialect. That flag however should not affect the *parsing* of inline assembly in the program. (See llvm.org/r322652)

When compiling normally, AsmPrinter::emitInlineAsm is used for assembling and defaults to At&t dialect. However, when compiling for ThinLTO, the code which parses module level inline asm to find symbols for the symbol table was failing to set the dialect. This patch fixes that. (See PR46503)


https://reviews.llvm.org/D82862

Files:
  clang/test/CodeGen/thinlto-inline-asm.c
  llvm/lib/Object/ModuleSymbolTable.cpp


Index: llvm/lib/Object/ModuleSymbolTable.cpp
===================================================================
--- llvm/lib/Object/ModuleSymbolTable.cpp
+++ llvm/lib/Object/ModuleSymbolTable.cpp
@@ -23,6 +23,7 @@
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/Module.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
@@ -116,6 +117,10 @@
   if (!TAP)
     return;
 
+  // Module-level inline asm is assumed to use At&t syntax (see
+  // AsmPrinter::doInitialization()).
+  Parser->setAssemblerDialect(InlineAsm::AD_ATT);
+
   Parser->setTargetParser(*TAP);
   if (Parser->Run(false))
     return;
Index: clang/test/CodeGen/thinlto-inline-asm.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/thinlto-inline-asm.c
@@ -0,0 +1,21 @@
+// REQUIRES: x86-registered-target
+
+// RUN: %clang_cc1 -triple x86_64-pc-windows-msvc19.11.0 -emit-llvm-bc \
+// RUN:   -flto=thin -mllvm -x86-asm-syntax=intel -v \
+// RUN:   -o %t.obj %s 2>&1 | FileCheck --check-prefix=CLANG %s
+//
+// RUN: llvm-lto2 dump-symtab %t.obj | FileCheck --check-prefix=SYMTAB %s
+
+// Module-level inline asm is parsed with At&t syntax. Test that the
+// -x86-asm-syntax flag does not affect this.
+
+// CLANG-NOT: unknown token in expression
+// SYMTAB: D------X foo
+// SYMTAB: D------X bar
+
+void foo() {}
+
+asm(".globl bar      \n"
+    "bar:            \n"
+    "  xor %eax, %eax\n"
+    "  ret           \n");


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