Great! If the extra special case doesn’t make the option ambiguous about what it is doing, I am happier with this approach. Here is the patch.
commit 9dd3fdfa3a90687e46c4731c9d23f4f1885a23f9 Author: Steven Wu <[email protected]> Date: Mon May 11 16:47:27 2015 -0700 Allow empty assembly string literal with -fno-gnu-inline-asm Empty assembly string will not introduce assembly code in the output binary and it is often used as a trick in the header to disable optimizations. It doesn't conflict with the purpose of the option so it is allowed with -fno-gnu-inline-asm flag. diff --git a/lib/Parse/Parser.cpp b/lib/Parse/Parser.cpp index ed27a9e..697fda9 100644 --- a/lib/Parse/Parser.cpp +++ b/lib/Parse/Parser.cpp @@ -670,12 +670,17 @@ Parser::ParseExternalDeclaration(ParsedAttributesWithRange &attrs, SourceLocation StartLoc = Tok.getLocation(); SourceLocation EndLoc; - // Check if GNU-style InlineAsm is disabled. - if (!getLangOpts().GNUAsm) - Diag(StartLoc, diag::err_gnu_inline_asm_disabled); - ExprResult Result(ParseSimpleAsm(&EndLoc)); + // Check if GNU-style InlineAsm is disabled. + // Empty asm string is allowed because it will not introduce + // any assembly code. + if (!(getLangOpts().GNUAsm || Result.isInvalid())) { + const auto *SL = cast<StringLiteral>(Result.get()); + if (!SL->getString().trim().empty()) + Diag(StartLoc, diag::err_gnu_inline_asm_disabled); + } + ExpectAndConsume(tok::semi, diag::err_expected_after, "top-level asm block"); diff --git a/test/Parser/no-gnu-inline-asm.c b/test/Parser/no-gnu-inline-asm.c index 7089fa4..7a13f20 100644 --- a/test/Parser/no-gnu-inline-asm.c +++ b/test/Parser/no-gnu-inline-asm.c @@ -5,6 +5,8 @@ asm ("INST r1, 0"); // expected-error {{GNU-style inline assembly is disabled}} void foo() __asm("__foo_func"); // AsmLabel is OK int foo1 asm("bar1") = 0; // OK +asm(" "); // Whitespace is OK + void f (void) { long long foo = 0, bar; asm volatile("INST %0, %1" : "=r"(foo) : "r"(bar)); // expected-error {{GNU-style inline assembly is disabled}} > On May 11, 2015, at 4:18 PM, Reid Kleckner <[email protected]> wrote: > > I think it might be better to special case empty or white-space only inline > asm. That way this flag actually tells you that the .ll file produced doesn't > have any instructions already baked into it. > > > REPOSITORY > rL LLVM > > http://reviews.llvm.org/D9679 > > EMAIL PREFERENCES > http://reviews.llvm.org/settings/panel/emailpreferences/ > > _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
