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Make sure to set trunc store action to Expand for all X86 targets.
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Authored by luqmana on Aug 29 2014, 11:56 AM.

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nadav
Summary

When compiling without SSE2, isTruncStoreLegal(F64, F32) would return Legal, whereas with SSE2 it would return Expand. And since the Target doesn't seem to actually handle a truncstore for double -> float, it would just output a store of a full double in the space for a float hence overwriting other bits on the stack.

define void @bar() unnamed_addr {
entry-block:
  %a = alloca double
  %b = alloca float

  store double 3.140000e+00, double* %a
  %0 = load double* %a

  %1 = fptrunc double %0 to float
  store float %1, float* %b

  ret void
}

Without SSE2:

bar:                                    # @bar
    .cfi_startproc
# BB#0:                                 # %entry-block
    subl    $20, %esp
.Ltmp0:
    .cfi_def_cfa_offset 24
    movl    $1074339512, 12(%esp)   # imm = 0x40091EB8
    movl    $1374389535, 8(%esp)    # imm = 0x51EB851F                 0x40091EB851EB851F (double) 3.14
    movl    $1074339512, 8(%esp)    # imm = 0x40091EB8
    movl    $1374389535, 4(%esp)    # imm = 0x51EB851F
    addl    $20, %esp
    retl

With SSE2:

bar:                                    # @bar
    .cfi_startproc
# BB#0:                                 # %entry-block
    subl    $20, %esp
.Ltmp0:
    .cfi_def_cfa_offset 24
    movl    $1074339512, 12(%esp)   # imm = 0x40091EB8
    movl    $1374389535, 8(%esp)    # imm = 0x51EB851F            0x40091EB851EB851F (double) 3.14
    movl    $1078523331, 4(%esp)    # imm = 0x4048F5C3           0x4048F5C3 (float) 3.14
    addl    $20, %esp
    retl

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Event Timeline

luqmana updated this revision to Diff 13098.Aug 29 2014, 11:56 AM
luqmana retitled this revision from to Make sure to set trunc store action to Expand for all X86 targets..
luqmana updated this object.
luqmana edited the test plan for this revision. (Show Details)
luqmana added a subscriber: Unknown Object (MLST).

Cool thanks! Could someone commit this for me?

luqmana abandoned this revision.Apr 22 2015, 7:55 AM