https://gcc.gnu.org/g:d7f7353440ff3c6856cf1bfb4bb79c86ed4c3efe
commit d7f7353440ff3c6856cf1bfb4bb79c86ed4c3efe
Author: Shreya Munnangi <smunnan...@ventanamicro.com>
Date: Thu Jul 3 21:03:03 2025 -0600
[RISC-V] Add basic instrumentation to fusion detection
We were looking to evaluate some changes from Artemiy that improve GCC's
ability to discover fusible instruction pairs. There was no good way to get
any static data out of the compiler about what kinds of fusions were
happening.
Yea, you could grub around the .sched dumps looking for the magic '+'
annotation, then look around at the slim RTL representation and make an
educated guess about what fused. But boy that was inconvenient.
All we really needed was a quick note in the dump file that the target hook
found a fusion pair and what kind was discovered. That made it easy to spot
invalid fusions, evaluate the effectiveness of Artemiy's work,
write/discover
testcases for existing fusions and implement new fusions.
So from a codegen standpoint this is NFC, it only affects dump file output.
It's gone through the usual testing and I'll wait for pre-commit CI to churn
through it before moving forward.
gcc/
* config/riscv/riscv.cc (riscv_macro_fusion_pair_p): Add basic
instrumentation to all cases where fusion is detected. Fix
minor formatting goofs found in the process.
(cherry picked from commit 053a678cc59a0c8adbdbb78802ff33a619b57b41)
Diff:
---
gcc/config/riscv/riscv.cc | 80 +++++++++++++++++++++++++++++++++++++----------
1 file changed, 64 insertions(+), 16 deletions(-)
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 8fa1082f7c13..167e78d41ef4 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -10253,11 +10253,15 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn
*curr)
&& CONST_INT_P (XEXP (SET_SRC (prev_set), 1))
&& CONST_INT_P (XEXP (SET_SRC (curr_set), 1))
&& INTVAL (XEXP (SET_SRC (prev_set), 1)) == 32
- && (( INTVAL (XEXP (SET_SRC (curr_set), 1)) == 32
- && riscv_fusion_enabled_p(RISCV_FUSE_ZEXTW) )
- || ( INTVAL (XEXP (SET_SRC (curr_set), 1)) < 32
- && riscv_fusion_enabled_p(RISCV_FUSE_ZEXTWS))))
- return true;
+ && ((INTVAL (XEXP (SET_SRC (curr_set), 1)) == 32
+ && riscv_fusion_enabled_p (RISCV_FUSE_ZEXTW) )
+ || (INTVAL (XEXP (SET_SRC (curr_set), 1)) < 32
+ && riscv_fusion_enabled_p (RISCV_FUSE_ZEXTWS))))
+ {
+ if (dump_file)
+ fprintf (dump_file, "RISCV_FUSE_ZEXTWS\n");
+ return true;
+ }
}
if (simple_sets_p && riscv_fusion_enabled_p (RISCV_FUSE_ZEXTH)
@@ -10278,7 +10282,11 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn
*curr)
&& CONST_INT_P (XEXP (SET_SRC (curr_set), 1))
&& INTVAL (XEXP (SET_SRC (prev_set), 1)) == 48
&& INTVAL (XEXP (SET_SRC (curr_set), 1)) == 48)
- return true;
+ {
+ if (dump_file)
+ fprintf (dump_file,"RISCV_FUSE_ZEXTH\n");
+ return true;
+ }
}
if (simple_sets_p && riscv_fusion_enabled_p (RISCV_FUSE_LDINDEXED)
@@ -10297,7 +10305,11 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn
*curr)
&& GET_CODE (SET_SRC (prev_set)) == PLUS
&& REG_P (XEXP (SET_SRC (prev_set), 0))
&& REG_P (XEXP (SET_SRC (prev_set), 1)))
- return true;
+ {
+ if (dump_file)
+ fprintf (dump_file, "RISCV_FUSE_LDINDEXED\n");
+ return true;
+ }
/* We are trying to match the following:
prev (add) == (set (reg:DI rD)
@@ -10313,7 +10325,11 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn
*curr)
&& GET_CODE (SET_SRC (prev_set)) == PLUS
&& REG_P (XEXP (SET_SRC (prev_set), 0))
&& REG_P (XEXP (SET_SRC (prev_set), 1)))
- return true;
+ {
+ if (dump_file)
+ fprintf (dump_file, "RISCV_FUSE_LDINDEXED\n");
+ return true;
+ }
}
if (simple_sets_p && riscv_fusion_enabled_p (RISCV_FUSE_LDPREINCREMENT)
@@ -10332,7 +10348,11 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn
*curr)
&& GET_CODE (SET_SRC (prev_set)) == PLUS
&& REG_P (XEXP (SET_SRC (prev_set), 0))
&& CONST_INT_P (XEXP (SET_SRC (prev_set), 1)))
- return true;
+ {
+ if (dump_file)
+ fprintf (dump_file, "RISCV_FUSE_LDPREINCREMENT\n");
+ return true;
+ }
}
if (simple_sets_p && riscv_fusion_enabled_p (RISCV_FUSE_LUI_ADDI)
@@ -10350,7 +10370,11 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn
*curr)
&& (GET_CODE (SET_SRC (prev_set)) == HIGH
|| (CONST_INT_P (SET_SRC (prev_set))
&& LUI_OPERAND (INTVAL (SET_SRC (prev_set))))))
- return true;
+ {
+ if (dump_file)
+ fprintf (dump_file, "RISCV_FUSE_LUI_ADDI\n");
+ return true;
+ }
}
if (simple_sets_p && riscv_fusion_enabled_p (RISCV_FUSE_AUIPC_ADDI)
@@ -10372,7 +10396,11 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn
*curr)
&& CONST_INT_P (XEXP (SET_SRC (curr_set), 1))
&& SMALL_OPERAND (INTVAL (XEXP (SET_SRC (curr_set), 1))))))
- return true;
+ {
+ if (dump_file)
+ fprintf (dump_file, "RISCV_FUSE_AUIPC_ADDI\n");
+ return true;
+ }
}
if (simple_sets_p && riscv_fusion_enabled_p (RISCV_FUSE_LUI_LD)
@@ -10392,14 +10420,22 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn
*curr)
&& SCALAR_INT_MODE_P (GET_MODE (SET_DEST (curr_set)))
&& GET_CODE (XEXP (SET_SRC (curr_set), 0)) == PLUS
&& REGNO (XEXP (XEXP (SET_SRC (curr_set), 0), 0)) == prev_dest_regno)
- return true;
+ {
+ if (dump_file)
+ fprintf (dump_file, "RISCV_FUSE_LUI_LD\n");
+ return true;
+ }
if (GET_CODE (SET_SRC (prev_set)) == HIGH
&& MEM_P (SET_SRC (curr_set))
&& SCALAR_INT_MODE_P (GET_MODE (SET_DEST (curr_set)))
&& GET_CODE (XEXP (SET_SRC (curr_set), 0)) == LO_SUM
&& REGNO (XEXP (XEXP (SET_SRC (curr_set), 0), 0)) == prev_dest_regno)
- return true;
+ {
+ if (dump_file)
+ fprintf (dump_file, "RISCV_FUSE_LUI_LD\n");
+ return true;
+ }
if (GET_CODE (SET_SRC (prev_set)) == HIGH
&& (GET_CODE (SET_SRC (curr_set)) == SIGN_EXTEND
@@ -10409,7 +10445,11 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn
*curr)
&& (GET_CODE (XEXP (XEXP (SET_SRC (curr_set), 0), 0)) == LO_SUM
&& (REGNO (XEXP (XEXP (XEXP (SET_SRC (curr_set), 0), 0), 0))
== prev_dest_regno)))
- return true;
+ {
+ if (dump_file)
+ fprintf (dump_file, "RISCV_FUSE_LUI_LD\n");
+ return true;
+ }
}
if (simple_sets_p && riscv_fusion_enabled_p (RISCV_FUSE_AUIPC_LD)
@@ -10425,7 +10465,11 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn
*curr)
&& MEM_P (SET_SRC (curr_set))
&& SCALAR_INT_MODE_P (GET_MODE (SET_DEST (curr_set)))
&& GET_CODE (XEXP (SET_SRC (curr_set), 0)) == PLUS)
- return true;
+ {
+ if (dump_file)
+ fprintf (dump_file, "RISCV_FUSE_AUIPC_LD\n");
+ return true;
+ }
}
if (simple_sets_p && riscv_fusion_enabled_p (RISCV_FUSE_ALIGNED_STD))
@@ -10473,7 +10517,11 @@ riscv_macro_fusion_pair_p (rtx_insn *prev, rtx_insn
*curr)
lower offset. */
if ((INTVAL (offset_prev) % 16) == 0
&& (INTVAL (offset_prev) + 8 == INTVAL (offset_curr)))
- return true;
+ {
+ if (dump_file)
+ fprintf (dump_file, "RISCV_FUSE_ALIGNED_STD\n");
+ return true;
+ }
}
}
}
