| Message ID | 7e28ba70-d18d-13ad-78bc-6e97ea6796a3@suse.com |
|---|---|
| State | New |
| Headers | show |
| Series | x86: (mainly) "prefix_extra" adjustments | expand |
On Thu, Aug 3, 2023 at 4:10 PM Jan Beulich via Gcc-patches <gcc-patches@gcc.gnu.org> wrote: > > Drop SSE5 leftovers from both its comment and its default calculation. > A value of 2 simply cannot occur anymore. Instead extend the comment to > mention the use of the attribute in "length_vex", clarifying why > "prefix_extra" can actually be meaningful on VEX-encoded insns despite > those not having any real prefixes except possibly segment overrides. > Ok. > gcc/ > > * config/i386/i386.md (prefix_extra): Correct comment. Fold > cases yielding 2 into ones yielding 1. > --- > I question the 3DNow! aspect here: There's no extra prefix there. It's > an immediate instead which "sub-divides" major opcode 0f0f. > > --- a/gcc/config/i386/i386.md > +++ b/gcc/config/i386/i386.md > @@ -620,13 +620,11 @@ > (const_int 0))) > > ;; There are also additional prefixes in 3DNOW, SSSE3. > -;; ssemuladd,sse4arg default to 0f24/0f25 and DREX byte, > -;; sseiadd1,ssecvt1 to 0f7a with no DREX byte. > ;; 3DNOW has 0f0f prefix, SSSE3 and SSE4_{1,2} 0f38/0f3a. > +;; While generally inapplicable to VEX/XOP/EVEX encodings, "length_vex" uses > +;; the attribute evaluating to zero to know that VEX2 encoding may be usable. > (define_attr "prefix_extra" "" > - (cond [(eq_attr "type" "ssemuladd,sse4arg") > - (const_int 2) > - (eq_attr "type" "sseiadd1,ssecvt1") > + (cond [(eq_attr "type" "ssemuladd,sse4arg,sseiadd1,ssecvt1") > (const_int 1) > ] > (const_int 0))) >
--- a/gcc/config/i386/i386.md +++ b/gcc/config/i386/i386.md @@ -620,13 +620,11 @@ (const_int 0))) ;; There are also additional prefixes in 3DNOW, SSSE3. -;; ssemuladd,sse4arg default to 0f24/0f25 and DREX byte, -;; sseiadd1,ssecvt1 to 0f7a with no DREX byte. ;; 3DNOW has 0f0f prefix, SSSE3 and SSE4_{1,2} 0f38/0f3a. +;; While generally inapplicable to VEX/XOP/EVEX encodings, "length_vex" uses +;; the attribute evaluating to zero to know that VEX2 encoding may be usable. (define_attr "prefix_extra" "" - (cond [(eq_attr "type" "ssemuladd,sse4arg") - (const_int 2) - (eq_attr "type" "sseiadd1,ssecvt1") + (cond [(eq_attr "type" "ssemuladd,sse4arg,sseiadd1,ssecvt1") (const_int 1) ] (const_int 0)))