https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102178
--- Comment #32 from Richard Biener <rguenth at gcc dot gnu.org> ---
So the bad "head" can be fixed via
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index c74edd1aaef..8f9f26e0a82 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -3580,9 +3580,9 @@
;; Possible store forwarding (partial memory) stall in alternatives 4, 6 and
7.
(define_insn "*movdf_internal"
[(set (match_operand:DF 0 "nonimmediate_operand"
- "=Yf*f,m ,Yf*f,?r ,!o,?*r ,!o,!o,?r,?m,?r,?r,v,v,v,m,*x,*x,*x,m ,r ,v,r
,o ,r ,m")
+ "=Yf*f,m ,Yf*f,?r ,!o,?*r ,!o,!o,?r,?m,?r,?r,v,v,v,m,*x,*x,*x,m ,!r,!v,r
,o ,r ,m")
(match_operand:DF 1 "general_operand"
- "Yf*fm,Yf*f,G ,roF,r ,*roF,*r,F ,rm,rC,C ,F ,C,v,m,v,C ,*x,m ,*x,v,r
,roF,rF,rmF,rC"))]
+ "Yf*fm,Yf*f,G ,roF,r ,*roF,*r,F ,rm,rC,C ,F ,C,v,m,v,C ,*x,m
,*x,!v,!r,roF,rF,rmF,rC"))]
"!(MEM_P (operands[0]) && MEM_P (operands[1]))
&& (lra_in_progress || reload_completed
|| !CONST_DOUBLE_P (operands[1])
which is adding ! to r<->v alternatives. That should eventually be done
by duplicating the alternatives and enabling one set via some enable
attribute based on some tunable. I see those alternatives are already
(set (attr "preferred_for_speed")
(cond [(eq_attr "alternative" "3,4")
(symbol_ref "TARGET_INTEGER_DFMODE_MOVES")
(eq_attr "alternative" "20")
(symbol_ref "TARGET_INTER_UNIT_MOVES_FROM_VEC")
(eq_attr "alternative" "21")
(symbol_ref "TARGET_INTER_UNIT_MOVES_TO_VEC")
]
(symbol_ref "true")))
not sure why it's preferred_for_speed here though - shouldn't that be
enabled for size if !TARGET_INTER_UNIT_MOVES_{TO,FROM}_VEC and otherwise
disabled? Not sure if combining enabled and preferred_for_speed is
reasonably possible, but we have a preferred_for_size attribute here.
The diff with ! added is quite short, I've yet have to measure any
effect on LBM:
--- streamcollide.s.orig 2022-04-25 11:37:01.638733951 +0200
+++ streamcollide.s2 2022-04-25 11:35:54.885849296 +0200
@@ -33,28 +33,24 @@
.p2align 4
.p2align 3
.L12:
- movq .LC0(%rip), %rax
- vmovsd .LC4(%rip), %xmm6
+ vmovsd .LC0(%rip), %xmm2
+ vmovsd .LC1(%rip), %xmm13
+ movabsq $0x3ff01878b7a1c25d, %rax
movabsq $0x3fef85af6c69b5a6, %rdi
+ vmovsd .LC2(%rip), %xmm12
+ vmovsd .LC3(%rip), %xmm14
movabsq $0x3ff03db8fde2ef4e, %r8
+ movabsq $0x3fefcea39c51dabe, %r9
+ vmovsd .LC4(%rip), %xmm6
vmovsd .LC5(%rip), %xmm7
movq .LC8(%rip), %r11
- movabsq $0x3fefcea39c51dabe, %r9
movq .LC6(%rip), %rdx
movq .LC7(%rip), %rcx
- vmovq %rax, %xmm2
- vmovq %rax, %xmm4
- movq .LC1(%rip), %rax
movq %r11, %rsi
movq %r11, %r12
- vmovq %rax, %xmm13
- vmovq %rax, %xmm8
- movq .LC2(%rip), %rax
- vmovq %rax, %xmm12
- vmovq %rax, %xmm5
- movq .LC3(%rip), %rax
- vmovq %rax, %xmm14
- movabsq $0x3ff01878b7a1c25d, %rax
+ vmovsd %xmm2, %xmm2, %xmm4
+ vmovsd %xmm13, %xmm13, %xmm8
+ vmovsd %xmm12, %xmm12, %xmm5
vmovsd %xmm14, -16(%rsp)
.L5:
vmulsd .LC9(%rip), %xmm0, %xmm3
