[LLVMbugs] [Bug 16334] New: NVPTX generates PTX that prevent the driver to use certain instructions

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Fri Jun 14 17:51:04 PDT 2013


            Bug ID: 16334
           Summary: NVPTX generates PTX that prevent the driver to use
                    certain instructions
           Product: tools
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: llc
          Assignee: unassignedbugs at nondot.org
          Reporter: fwinter at jlab.org
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 10681
  --> http://llvm.org/bugs/attachment.cgi?id=10681&action=edit

NVPTX generates code that hinders the compute compiler to generate certain,
optimized instructions, like ISCADD.

The attached kernel (cmplx_mul_ir_builder.ll) compiles with libnvvm and the
compute compiler to

        /*0038*/            @P0 ISCADD R6, R0, c[0x0][0x14c], 0x2;          /*
0x60c008002980001a */
0x08a0bc8c8c10a010 */
        /*0048*/            @P0 ISCADD R7, R0, c[0x0][0x148], 0x2;          /*
0x60c008002900001e */
        /*0050*/            @P0 LD R5, [R6];                                /*
0xc400000000001814 */
        /*0058*/            @P0 ISCADD R0, R0, c[0x0][0x144], 0x2;          /*
0x60c0080028800002 */
        /*0060*/            @P0 LD R4, [R7];                                /*
0xc400000000001c10 */

Whereas NVPTX generates code that the driver compiles to

        /*0048*/            @P0 IADD R6, R0, 0x1000;                        /*
0xc080000800000019 */
        /*0050*/            @P0 IMAD R8.CC, R0, R7, c[0x0][0x150];          /*
0x910c1c002a000022 */
        /*0058*/            @P0 IMAD.HI.X R9, R0, R7, c[0x0][0x154];        /*
0x93181c002a800026 */
        /*0060*/            @P0 IMAD R14.CC, R6, R7, c[0x0][0x150];         /*
0x910c1c002a00183a */
        /*0068*/            @P0 LD.E R2, [R8];                              /*
0xc480000000002008 */

This might be just another symptom of bug 16333 or it is unrelated.

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