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cmd/compile: stop using fucomi* ops for 387 builds

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The fucomi* opcodes were only introduced for the Pentium Pro.
They do not exist for an MMX Pentium.  Use the fucom* instructions
instead and move the condition codes from the fp flags register to
the integer flags register explicitly.

The use of fucomi* opcodes in ggen.go was introduced in 1.5 (CL 8738).
The bad ops were generated for 64-bit floating-point comparisons.

The use of fucomi* opcodes in gsubr.go dates back to at least 1.1.
The bad ops were generated for float{32,64} to uint64 conversions.

Fixes #13923

Change-Id: I5290599f5edea8abf8fb18036f44fa78bd1fc9e6
Reviewed-on: https://go-review.googlesource.com/18590
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
This commit is contained in:
Keith Randall 2016-01-12 12:42:28 -08:00
parent f3ce054a44
commit 3d01f28e47
4 changed files with 120 additions and 11 deletions
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13
src/cmd/compile/internal/x86/gsubr.go
View file

@ -1198,14 +1198,17 @@ func floatmove(f *gc.Node, t *gc.Node) {
// if 0 > v { answer = 0 }
gins(x86.AFMOVD, &zerof, &f0)
gins(x86.AFUCOMIP, &f0, &f1)
gins(x86.AFUCOMP, &f0, &f1)
gins(x86.AFSTSW, nil, &ax)
gins(x86.ASAHF, nil, nil)
p1 := gc.Gbranch(optoas(gc.OGT, gc.Types[tt]), nil, 0)
// if 1<<64 <= v { answer = 0 too }
gins(x86.AFMOVD, &two64f, &f0)
gins(x86.AFUCOMIP, &f0, &f1)
gins(x86.AFUCOMP, &f0, &f1)
gins(x86.AFSTSW, nil, &ax)
gins(x86.ASAHF, nil, nil)
p2 := gc.Gbranch(optoas(gc.OGT, gc.Types[tt]), nil, 0)
gc.Patch(p1, gc.Pc)
gins(x86.AFMOVVP, &f0, t) // don't care about t, but will pop the stack
@ -1235,7 +1238,9 @@ func floatmove(f *gc.Node, t *gc.Node) {
// actual work
gins(x86.AFMOVD, &two63f, &f0)
gins(x86.AFUCOMIP, &f0, &f1)
gins(x86.AFUCOMP, &f0, &f1)
gins(x86.AFSTSW, nil, &ax)
gins(x86.ASAHF, nil, nil)
p2 = gc.Gbranch(optoas(gc.OLE, gc.Types[tt]), nil, 0)
gins(x86.AFMOVVP, &f0, t)
p3 := gc.Gbranch(obj.AJMP, nil, 0)