en Copyright 2015 Java http://172.16.0.5:8080/history/llvm-project-15.0.7/clang/test/Sema/asm-goto.cpp#50cac248 Support output constraints on "asm goto"Summary:Clang's "asm goto" feature didn't initially support outputs constraints. Thatwas the same behavior as gcc's implementation. The decision by gcc not tosupport outputs was based on a restriction in their IR regarding terminators.LLVM doesn't restrict terminators from returning values (e.g. 'invoke'), soit made sense to support this feature.Output values are valid only on the 'fallthrough' path. If an output value's usedon an indirect branch, then it's 'poisoned'.In theory, outputs *could* be valid on the 'indirect' paths, but it's verydifficult to guarantee that the original semantics would be retained. E.g.because indirect labels could be used as data, we wouldn't be able to splitcritical edges in situations where two 'callbr' instructions have the sameindirect label, because the indirect branch's destination would no longer bethe same.Reviewers: jyknight, nickdesaulniers, hfinkelReviewed By: jyknight, nickdesaulniersSubscribers: MaskRay, rsmith, hiraditya, llvm-commits, cfe-commits, craig.topper, rnkTags: #clang, #llvmDifferential Revision: https://reviews.llvm.org/D69876 List of files: /llvm-project-15.0.7/clang/test/Sema/asm-goto.cpp Tue, 25 Feb 2020 02:32:50 +0000 Bill Wendling <isanbard@gmail.com> http://172.16.0.5:8080/history/llvm-project-15.0.7/clang/test/Sema/asm-goto.cpp#b8fee677 Re-check in clang support gun asm goto after fixing tests.llvm-svn: 362410 List of files: /llvm-project-15.0.7/clang/test/Sema/asm-goto.cpp Mon, 03 Jun 2019 15:57:25 +0000 Jennifer Yu <jennifer.yu@intel.com> http://172.16.0.5:8080/history/llvm-project-15.0.7/clang/test/Sema/asm-goto.cpp#954ec09a clang support gnu asm goto.Syntax: asm [volatile] goto ( AssemblerTemplate : : InputOperands : Clobbers : GotoLabels)https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.htmlNew llvm IR is "callbr" for inline asm goto instead "call" for inline asmFor:asm goto("testl %0, %0; jne %l1;" :: "r"(cond)::label_true, loop);IR:callbr void asm sideeffect "testl $0, $0; jne ${1:l};", "r,X,X,~{dirflag},~{fpsr},~{flags}"(i32 %0, i8* blockaddress(@foo, %label_true), i8* blockaddress(@foo, %loop)) #1 to label %asm.fallthrough [label %label_true, label %loop], !srcloc !3asm.fallthrough: Compiler need to generate:1> a dummy constarint 'X' for each label.2> an unique fallthrough label for each asm goto stmt " asm.fallthrough%number".Diagnostic 1> duplicate asm operand name are used in output, input and label.2> goto out of scope.llvm-svn: 362045 List of files: /llvm-project-15.0.7/clang/test/Sema/asm-goto.cpp Thu, 30 May 2019 01:05:46 +0000 Jennifer Yu <jennifer.yu@intel.com>