This patch refactors the three places in the i386.md backend that we
set the carry flag into a new ix86_expand_carry helper function, that
allows Jakub's recently added uaddc<mode>5 and usubc<mode>5 expanders
to take advantage of the recently added support for the stc instruction.
This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
and make -k check, both with and without --target_board=unix{-m32}
with no new failures. Ok for mainline?
2023-06-18 Roger Sayle <ro...@nextmovesoftware.com>
gcc/ChangeLog
* config/i386/i386-expand.cc (ix86_expand_carry): New helper
function for setting the carry flag.
(ix86_expand_builtin) <handlecarry>: Use it here.
* config/i386/i386-protos.h (ix86_expand_carry): Prototype here.
* config/i386/i386.md (uaddc<mode>5): Use ix86_expand_carry.
(usubc<mode>5): Likewise.
Thanks in advance,
Roger
--
diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
index def060a..3d5eca6 100644
--- a/gcc/config/i386/i386-expand.cc
+++ b/gcc/config/i386/i386-expand.cc
@@ -12644,6 +12644,21 @@ ix86_check_builtin_isa_match (unsigned int fcode,
return (bisa & isa) == bisa && (bisa2 & isa2) == bisa2;
}
+/* Emit instructions to set the carry flag from ARG. */
+
+void
+ix86_expand_carry (rtx arg)
+{
+ if (!CONST_INT_P (arg) || arg == const0_rtx)
+ {
+ arg = convert_to_mode (QImode, arg, 1);
+ arg = copy_to_mode_reg (QImode, arg);
+ emit_insn (gen_addqi3_cconly_overflow (arg, constm1_rtx));
+ }
+ else
+ emit_insn (gen_x86_stc ());
+}
+
/* Expand an expression EXP that calls a built-in function,
with result going to TARGET if that's convenient
(and in mode MODE if that's convenient).
@@ -13975,14 +13990,7 @@ rdseed_step:
else
{
/* Generate CF from input operand. */
- if (!CONST_INT_P (op1))
- {
- op1 = convert_to_mode (QImode, op1, 1);
- op1 = copy_to_mode_reg (QImode, op1);
- emit_insn (gen_addqi3_cconly_overflow (op1, constm1_rtx));
- }
- else
- emit_insn (gen_x86_stc ());
+ ix86_expand_carry (op1);
/* Generate instruction that consumes CF. */
op1 = gen_rtx_REG (CCCmode, FLAGS_REG);
diff --git a/gcc/config/i386/i386-protos.h b/gcc/config/i386/i386-protos.h
index af01299..27fe73c 100644
--- a/gcc/config/i386/i386-protos.h
+++ b/gcc/config/i386/i386-protos.h
@@ -155,6 +155,7 @@ extern void ix86_expand_sse_movcc (rtx, rtx, rtx, rtx);
extern void ix86_expand_sse_unpack (rtx, rtx, bool, bool);
extern void ix86_expand_fp_spaceship (rtx, rtx, rtx);
extern bool ix86_expand_int_addcc (rtx[]);
+extern void ix86_expand_carry (rtx arg);
extern rtx_insn *ix86_expand_call (rtx, rtx, rtx, rtx, rtx, bool);
extern bool ix86_call_use_plt_p (rtx);
extern void ix86_split_call_vzeroupper (rtx, rtx);
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 93794c1..a50cbc8 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -8601,9 +8601,7 @@
emit_insn (gen_addcarry<mode>_0 (operands[0], operands[2], operands[3]));
else
{
- rtx op4 = copy_to_mode_reg (QImode,
- convert_to_mode (QImode, operands[4], 1));
- emit_insn (gen_addqi3_cconly_overflow (op4, constm1_rtx));
+ ix86_expand_carry (operands[4]);
pat = gen_rtx_LTU (<DWI>mode, cf, const0_rtx);
pat2 = gen_rtx_LTU (<MODE>mode, cf, const0_rtx);
emit_insn (gen_addcarry<mode> (operands[0], operands[2], operands[3],
@@ -8634,9 +8632,7 @@
else
{
cf = gen_rtx_REG (CCCmode, FLAGS_REG);
- rtx op4 = copy_to_mode_reg (QImode,
- convert_to_mode (QImode, operands[4], 1));
- emit_insn (gen_addqi3_cconly_overflow (op4, constm1_rtx));
+ ix86_expand_carry (operands[4]);
pat = gen_rtx_LTU (<DWI>mode, cf, const0_rtx);
pat2 = gen_rtx_LTU (<MODE>mode, cf, const0_rtx);
emit_insn (gen_subborrow<mode> (operands[0], operands[2], operands[3],
