https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96403
Tom de Vries <vries at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target| |nvptx
--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
Looking at the first regression, we have without the patch:
...
//(insn 9 5 12 2
// (set (reg:HI 27 [ arg ])
// (subreg:HI (reg/v:V2SI 25 [ arg ]) 0))
// "v2si-cvt.c":11:32 5 {*movhi_insn}
// (nil))
cvt.u16.u32 %r27, %r25.x; // 9 [c=12] *movhi_insn/0
...
and with the patch:
...
//(insn 8 5 9 2
// (set (reg:DI 26 [ arg ])
// (subreg:DI (reg/v:V2SI 25 [ arg ]) 0))
// "v2si-cvt.c":11:32 7 {*movdi_insn}
// (nil))
mov.b64 %r26, %r25; // 8 [c=12] *movdi_insn/0
//(insn 9 8 13 2
// (set (reg:HI 27 [ arg ])
// (truncate:HI (reg:DI 26 [ arg ])))
// "v2si-cvt.c":11:32 32 {truncdihi2}
// (expr_list:REG_DEAD (reg:DI 26 [ arg ])
// (nil)))
cvt.u16.u64 %r27, %r26;
...
I guess we would like to generate this instead:
...
//(insn 9 8 13 2
// (set (reg:HI 27 [ arg ])
// (truncate:HI (subreg:SI (reg/v:V2SI 25 [ arg ]) 0))
// "v2si-cvt.c":11:32 32 {truncdihi2}
// (expr_list:REG_DEAD (reg:DI 26 [ arg ])
// (nil)))
cvt.u16.u32 %r26, %r25.x;
...
Debugging combine, we hit TARGET_MODES_TIEABLE_P as a barrier, but after
enabling that we have a slightly different inns (the store has merged with the
truncate), where combine also fails:
...
Trying 8 -> 13:
8: r26:DI=r25:V2SI#0
13: [%frame:DI]=trunc(r26:DI)
REG_DEAD r26:DI
Failed to match this instruction:
(set (mem/v/c:HI (reg/f:DI 2 %frame) [2 s+0 S2 A128])
(truncate:HI (subreg:DI (reg/v:V2SI 25 [ arg ]) 0)))
...
I've tried enabling subregs in truncsi<HI> but that didn't help either.
I managed to get the desired code using this (to match the pattern tried by
combine):
...
@@ -372,11 +386,26 @@
(define_insn "truncdi<mode>2"
[(set (match_operand:QHSIM 0 "nvptx_nonimmediate_operand" "=R,m")
- (truncate:QHSIM (match_operand:DI 1 "nvptx_register_operand" "R,R")))]
+ (truncate:QHSIM (match_operand:DI 1 "register_operand" "R,Q")))]
""
- "@
- %.\\tcvt%t0.u64\\t%0, %1;
- %.\\tst%A0.u%T0\\t%0, %1;"
+{
+ if (which_alternative == 0)
+ {
+ if (SUBREG_P (operands[1])
+ && GET_MODE (SUBREG_REG (operands[1])) == V2SImode)
+ return "%.\\tcvt%t0.u32\\t%0, %1.x;";
+ else
+ return "%.\\tcvt%t0.u64\\t%0, %1;";
+ }
+ else
+ {
+ if (SUBREG_P (operands[1])
+ && GET_MODE (SUBREG_REG (operands[1])) == V2SImode)
+ return " %.\\tst%A0.u%T0\\t%0, %1.x;";
+ else
+ return " %.\\tst%A0.u%T0\\t%0, %1;";
+ }
+}
[(set_attr "subregs_ok" "true")])
;; Integer arithmetic
...
But I would hope there's a cleaner way.
