Stumbled upon this when trying to wholesale rewrite frm switching code
and seeing what pieces needed to be retained from current implementation.
My interpretation of how this hook worked, for the following case:
fsrmi 3
fsrm a4
call
frrm a4
fsrmi 1
TARGET_MODE_NEEDED(call_insn) returns DYN_EXIT (to generate fsrm) and
TARGET_MODE_AFTER(call_insn) returns DYN (to generate frrm). However
for a given insn, if the 2 hooks return different values, the final
state machine doesn't switch as expected above (and instead both NEEDED
and AFTER need to return the same mode, for most cases).
Anyhow it turns out that no-oping this (return the last_mode back) doesn't
change any testcase outcomes. There's no change to total number of FRM
read/writes emitted (static count) for SPEC2017 -Ofast -march=rv64gcv build
But we win again on reduced complexity and maintenance.
gcc/ChangeLog:
* config/riscv/riscv.cc (riscv_frm_mode_needed): Move static
state update here.
(frm_unknown_dynamic_p): Delete.
(riscv_frm_mode_after): Delete.
(riscv_mode_after): Remove call to riscv_frm_mode_after ().
Signed-off-by: Vineet Gupta <vine...@rivosinc.com>
---
gcc/config/riscv/riscv.cc | 43 +++++++--------------------------------
1 file changed, 7 insertions(+), 36 deletions(-)
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index a500b046cd9a..f1b4b20499fc 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -12193,6 +12193,8 @@ riscv_frm_mode_needed (rtx_insn *cur_insn, int code)
the emit mode set.
*/
mode = riscv_frm_adjust_mode_after_call (cur_insn, mode);
+ else if (riscv_static_frm_mode_p (mode))
+ STATIC_FRM_P (cfun) = true;
return mode;
}
@@ -12317,18 +12319,6 @@ vxrm_unknown_p (rtx_insn *insn)
return false;
}
-/* Return TRUE that an insn is unknown dynamic for FRM. */
-
-static bool
-frm_unknown_dynamic_p (rtx_insn *insn)
-{
- /* Return true if there is a definition of FRM. */
- if (reg_set_p (gen_rtx_REG (SImode, FRM_REGNUM), insn))
- return true;
-
- return false;
-}
-
/* Return the mode that an insn results in for VXRM. */
static int
@@ -12346,29 +12336,8 @@ riscv_vxrm_mode_after (rtx_insn *insn, int mode)
return mode;
}
-/* Return the mode that an insn results in for FRM. */
-
-static int
-riscv_frm_mode_after (rtx_insn *insn, int mode)
-{
- STATIC_FRM_P (cfun) = STATIC_FRM_P (cfun) || riscv_static_frm_mode_p (mode);
-
- if (CALL_P (insn))
- return mode;
-
- if (frm_unknown_dynamic_p (insn))
- return riscv_vector::FRM_DYN;
-
- if (recog_memoized (insn) < 0)
- return mode;
-
- if (reg_mentioned_p (gen_rtx_REG (SImode, FRM_REGNUM), PATTERN (insn)))
- return get_attr_frm_mode (insn);
- else
- return mode;
-}
-
-/* Return the mode that an insn results in. */
+/* Implement TARGET_MODE_AFTER.
+ Return the mode that an insn results in. */
static int
riscv_mode_after (int entity, int mode, rtx_insn *insn, HARD_REG_SET)
@@ -12377,8 +12346,10 @@ riscv_mode_after (int entity, int mode, rtx_insn
*insn, HARD_REG_SET)
{
case RISCV_VXRM:
return riscv_vxrm_mode_after (insn, mode);
+
+ /* FRM state machine doesn't need after insn handling. */
case RISCV_FRM:
- return riscv_frm_mode_after (insn, mode);
+ return mode;
default:
gcc_unreachable ();
}
--
2.43.0
