[LLVMbugs] [Bug 24200] New: With integrated assembler enabled, fail to fetch version string of assembler

[bugzilla-daemon at llvm.org]

https://llvm.org/bugs/show_bug.cgi?id=24200

            Bug ID: 24200
           Summary: With integrated assembler enabled, fail to fetch
                    version string of assembler
           Product: clang
           Version: 3.6
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Driver
          Assignee: unassignedclangbugs at nondot.org
          Reporter: noloader at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

We have a GNU makefile that mostly configures itself on the fly. The makefile
has tests like:

   GAS219_OR_LATER := $(shell $(CXX) -xc -c /dev/null -Wa,-v -o/dev/null 2>&1 |
$(EGREP) -i -c "GNU assembler version (2\.19|2\.[2-9]|[3-9])")

Later, if `GAS219_OR_LATER` is defined, then code paths that utilize SSE, SSE2,
SSE3, double-quad word multiply, AES-NI, etc are utilized.

However, clang does not return a version in response to the query. Rather, it
just errors out:

    $ clang++ -xc -c /dev/null -Wa,-v -o/dev/null 2>&1
    clang: error: unsupported argument '-v' to option 'Wa,'

This is how the assembler is supposed to react (give or take) when running it
through the GCC compiler driver:

    $ g++ -xc -c /dev/null -Wa,-v -o/dev/null 2>&1
    GNU assembler version 2.24 (x86_64-linux-gnu) using BFD version (GNU
Binutils for Ubuntu) 2.

Determining the assembler and its version is critical to us due to  issues like
https://llvm.org/bugs/show_bug.cgi?id=18916.

Please consume `-Wa,-v`, and please return a string to identify the integrated
assembler.

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