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* [gcc r14-405] RISC-V: Weaken LR/SC pairs
@ 2023-05-02 20:10 Patrick O'Neill
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From: Patrick O'Neill @ 2023-05-02 20:10 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:942ab49b5f8955371cf5db23608ba5f5f5244152
commit r14-405-g942ab49b5f8955371cf5db23608ba5f5f5244152
Author: Patrick O'Neill <patrick@rivosinc.com>
Date: Wed Apr 5 09:49:20 2023 -0700
RISC-V: Weaken LR/SC pairs
Introduce the %I and %J flags for setting the .aqrl bits on LR/SC pairs
as needed.
Atomic compare and exchange ops provide success and failure memory
models. C++17 and later place no restrictions on the relative strength
of each model, so ensure we cover both by using a model that enforces
the ordering of both given models.
This change brings LR/SC ops in line with table A.6 of the ISA manual.
2023-04-27 Patrick O'Neill <patrick@rivosinc.com>
gcc/ChangeLog:
* config/riscv/riscv-protos.h (riscv_union_memmodels): Expose
riscv_union_memmodels function to sync.md.
* config/riscv/riscv.cc (riscv_union_memmodels): Add function to
get the union of two memmodels in sync.md.
(riscv_print_operand): Add %I and %J flags that output the
optimal LR/SC flag bits for a given memory model.
* config/riscv/sync.md: Remove static .aqrl bits on LR op/.rl
bits on SC op and replace with optimized %I, %J flags.
Signed-off-by: Patrick O'Neill <patrick@rivosinc.com>
Diff:
---
gcc/config/riscv/riscv-protos.h | 3 ++
gcc/config/riscv/riscv.cc | 44 ++++++++++++++++
gcc/config/riscv/sync.md | 114 +++++++++++++++++++++++-----------------
3 files changed, 114 insertions(+), 47 deletions(-)
diff --git a/gcc/config/riscv/riscv-protos.h b/gcc/config/riscv/riscv-protos.h
index 5a927bdf1b0..33eb574aadc 100644
--- a/gcc/config/riscv/riscv-protos.h
+++ b/gcc/config/riscv/riscv-protos.h
@@ -22,6 +22,8 @@ along with GCC; see the file COPYING3. If not see
#ifndef GCC_RISCV_PROTOS_H
#define GCC_RISCV_PROTOS_H
+#include "memmodel.h"
+
/* Symbol types we understand. The order of this list must match that of
the unspec enum in riscv.md, subsequent to UNSPEC_ADDRESS_FIRST. */
enum riscv_symbol_type {
@@ -81,6 +83,7 @@ extern bool riscv_v_ext_vector_mode_p (machine_mode);
extern bool riscv_shamt_matches_mask_p (int, HOST_WIDE_INT);
extern void riscv_subword_address (rtx, rtx *, rtx *, rtx *, rtx *);
extern void riscv_lshift_subword (machine_mode, rtx, rtx, rtx *);
+extern enum memmodel riscv_union_memmodels (enum memmodel, enum memmodel);
/* Routines implemented in riscv-c.cc. */
void riscv_cpu_cpp_builtins (cpp_reader *);
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index ce79c9bf123..1e328f6a801 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -4294,6 +4294,36 @@ riscv_print_operand_reloc (FILE *file, rtx op, bool hi_reloc)
fputc (')', file);
}
+/* Return the memory model that encapuslates both given models. */
+
+enum memmodel
+riscv_union_memmodels (enum memmodel model1, enum memmodel model2)
+{
+ model1 = memmodel_base (model1);
+ model2 = memmodel_base (model2);
+
+ enum memmodel weaker = model1 <= model2 ? model1: model2;
+ enum memmodel stronger = model1 > model2 ? model1: model2;
+
+ switch (stronger)
+ {
+ case MEMMODEL_SEQ_CST:
+ case MEMMODEL_ACQ_REL:
+ return stronger;
+ case MEMMODEL_RELEASE:
+ if (weaker == MEMMODEL_ACQUIRE || weaker == MEMMODEL_CONSUME)
+ return MEMMODEL_ACQ_REL;
+ else
+ return stronger;
+ case MEMMODEL_ACQUIRE:
+ case MEMMODEL_CONSUME:
+ case MEMMODEL_RELAXED:
+ return stronger;
+ default:
+ gcc_unreachable ();
+ }
+}
+
/* Return true if the .AQ suffix should be added to an AMO to implement the
acquire portion of memory model MODEL. */
@@ -4347,6 +4377,8 @@ riscv_memmodel_needs_amo_release (enum memmodel model)
'R' Print the low-part relocation associated with OP.
'C' Print the integer branch condition for comparison OP.
'A' Print the atomic operation suffix for memory model OP.
+ 'I' Print the LR suffix for memory model OP.
+ 'J' Print the SC suffix for memory model OP.
'z' Print x0 if OP is zero, otherwise print OP normally.
'i' Print i if the operand is not a register.
'S' Print shift-index of single-bit mask OP.
@@ -4516,6 +4548,18 @@ riscv_print_operand (FILE *file, rtx op, int letter)
fputs (".rl", file);
break;
+ case 'I':
+ if (model == MEMMODEL_SEQ_CST)
+ fputs (".aqrl", file);
+ else if (riscv_memmodel_needs_amo_acquire (model))
+ fputs (".aq", file);
+ break;
+
+ case 'J':
+ if (riscv_memmodel_needs_amo_release (model))
+ fputs (".rl", file);
+ break;
+
case 'i':
if (code != REG)
fputs ("i", file);
diff --git a/gcc/config/riscv/sync.md b/gcc/config/riscv/sync.md
index 9a3b57bd09f..3e6345e83a3 100644
--- a/gcc/config/riscv/sync.md
+++ b/gcc/config/riscv/sync.md
@@ -116,21 +116,22 @@
(unspec_volatile:SI
[(any_atomic:SI (match_dup 1)
(match_operand:SI 2 "register_operand" "rI")) ;; value for op
- (match_operand:SI 3 "register_operand" "rI")] ;; mask
+ (match_operand:SI 3 "const_int_operand")] ;; model
UNSPEC_SYNC_OLD_OP_SUBWORD))
- (match_operand:SI 4 "register_operand" "rI") ;; not_mask
- (clobber (match_scratch:SI 5 "=&r")) ;; tmp_1
- (clobber (match_scratch:SI 6 "=&r"))] ;; tmp_2
+ (match_operand:SI 4 "register_operand" "rI") ;; mask
+ (match_operand:SI 5 "register_operand" "rI") ;; not_mask
+ (clobber (match_scratch:SI 6 "=&r")) ;; tmp_1
+ (clobber (match_scratch:SI 7 "=&r"))] ;; tmp_2
"TARGET_ATOMIC && TARGET_INLINE_SUBWORD_ATOMIC"
{
return "1:\;"
- "lr.w.aqrl\t%0, %1\;"
- "<insn>\t%5, %0, %2\;"
- "and\t%5, %5, %3\;"
- "and\t%6, %0, %4\;"
- "or\t%6, %6, %5\;"
- "sc.w.rl\t%5, %6, %1\;"
- "bnez\t%5, 1b";
+ "lr.w%I3\t%0, %1\;"
+ "<insn>\t%6, %0, %2\;"
+ "and\t%6, %6, %4\;"
+ "and\t%7, %0, %5\;"
+ "or\t%7, %7, %6\;"
+ "sc.w%J3\t%6, %7, %1\;"
+ "bnez\t%6, 1b";
}
[(set (attr "length") (const_int 28))])
@@ -151,6 +152,7 @@
rtx old = gen_reg_rtx (SImode);
rtx mem = operands[1];
rtx value = operands[2];
+ rtx model = operands[3];
rtx aligned_mem = gen_reg_rtx (SImode);
rtx shift = gen_reg_rtx (SImode);
rtx mask = gen_reg_rtx (SImode);
@@ -162,7 +164,7 @@
riscv_lshift_subword (<MODE>mode, value, shift, &shifted_value);
emit_insn (gen_subword_atomic_fetch_strong_nand (old, aligned_mem,
- shifted_value,
+ shifted_value, model,
mask, not_mask));
emit_move_insn (old, gen_rtx_ASHIFTRT (SImode, old,
@@ -180,22 +182,23 @@
(unspec_volatile:SI
[(not:SI (and:SI (match_dup 1)
(match_operand:SI 2 "register_operand" "rI"))) ;; value for op
- (match_operand:SI 3 "register_operand" "rI")] ;; mask
+ (match_operand:SI 3 "const_int_operand")] ;; mask
UNSPEC_SYNC_OLD_OP_SUBWORD))
- (match_operand:SI 4 "register_operand" "rI") ;; not_mask
- (clobber (match_scratch:SI 5 "=&r")) ;; tmp_1
- (clobber (match_scratch:SI 6 "=&r"))] ;; tmp_2
+ (match_operand:SI 4 "register_operand" "rI") ;; mask
+ (match_operand:SI 5 "register_operand" "rI") ;; not_mask
+ (clobber (match_scratch:SI 6 "=&r")) ;; tmp_1
+ (clobber (match_scratch:SI 7 "=&r"))] ;; tmp_2
"TARGET_ATOMIC && TARGET_INLINE_SUBWORD_ATOMIC"
{
return "1:\;"
- "lr.w.aqrl\t%0, %1\;"
- "and\t%5, %0, %2\;"
- "not\t%5, %5\;"
- "and\t%5, %5, %3\;"
- "and\t%6, %0, %4\;"
- "or\t%6, %6, %5\;"
- "sc.w.rl\t%5, %6, %1\;"
- "bnez\t%5, 1b";
+ "lr.w%I3\t%0, %1\;"
+ "and\t%6, %0, %2\;"
+ "not\t%6, %6\;"
+ "and\t%6, %6, %4\;"
+ "and\t%7, %0, %5\;"
+ "or\t%7, %7, %6\;"
+ "sc.w%J3\t%6, %7, %1\;"
+ "bnez\t%6, 1b";
}
[(set (attr "length") (const_int 32))])
@@ -216,6 +219,7 @@
rtx old = gen_reg_rtx (SImode);
rtx mem = operands[1];
rtx value = operands[2];
+ rtx model = operands[3];
rtx aligned_mem = gen_reg_rtx (SImode);
rtx shift = gen_reg_rtx (SImode);
rtx mask = gen_reg_rtx (SImode);
@@ -228,7 +232,8 @@
emit_insn (gen_subword_atomic_fetch_strong_<atomic_optab> (old, aligned_mem,
shifted_value,
- mask, not_mask));
+ model, mask,
+ not_mask));
emit_move_insn (old, gen_rtx_ASHIFTRT (SImode, old,
gen_lowpart (QImode, shift)));
@@ -261,6 +266,7 @@
rtx old = gen_reg_rtx (SImode);
rtx mem = operands[1];
rtx value = operands[2];
+ rtx model = operands[3];
rtx aligned_mem = gen_reg_rtx (SImode);
rtx shift = gen_reg_rtx (SImode);
rtx mask = gen_reg_rtx (SImode);
@@ -272,7 +278,8 @@
riscv_lshift_subword (<MODE>mode, value, shift, &shifted_value);
emit_insn (gen_subword_atomic_exchange_strong (old, aligned_mem,
- shifted_value, not_mask));
+ shifted_value, model,
+ not_mask));
emit_move_insn (old, gen_rtx_ASHIFTRT (SImode, old,
gen_lowpart (QImode, shift)));
@@ -286,18 +293,19 @@
(match_operand:SI 1 "memory_operand" "+A")) ;; mem location
(set (match_dup 1)
(unspec_volatile:SI
- [(match_operand:SI 2 "reg_or_0_operand" "rI") ;; value
- (match_operand:SI 3 "reg_or_0_operand" "rI")] ;; not_mask
+ [(match_operand:SI 2 "reg_or_0_operand" "rI") ;; value
+ (match_operand:SI 3 "const_int_operand")] ;; model
UNSPEC_SYNC_EXCHANGE_SUBWORD))
- (clobber (match_scratch:SI 4 "=&r"))] ;; tmp_1
+ (match_operand:SI 4 "reg_or_0_operand" "rI") ;; not_mask
+ (clobber (match_scratch:SI 5 "=&r"))] ;; tmp_1
"TARGET_ATOMIC && TARGET_INLINE_SUBWORD_ATOMIC"
{
return "1:\;"
- "lr.w.aqrl\t%0, %1\;"
- "and\t%4, %0, %3\;"
- "or\t%4, %4, %2\;"
- "sc.w.rl\t%4, %4, %1\;"
- "bnez\t%4, 1b";
+ "lr.w%I3\t%0, %1\;"
+ "and\t%5, %0, %4\;"
+ "or\t%5, %5, %2\;"
+ "sc.w%J3\t%5, %5, %1\;"
+ "bnez\t%5, 1b";
}
[(set (attr "length") (const_int 20))])
@@ -313,10 +321,15 @@
(clobber (match_scratch:GPR 6 "=&r"))]
"TARGET_ATOMIC"
{
+ enum memmodel model_success = (enum memmodel) INTVAL (operands[4]);
+ enum memmodel model_failure = (enum memmodel) INTVAL (operands[5]);
+ /* Find the union of the two memory models so we can satisfy both success
+ and failure memory models. */
+ operands[5] = GEN_INT (riscv_union_memmodels (model_success, model_failure));
return "1:\;"
- "lr.<amo>.aqrl\t%0,%1\;"
+ "lr.<amo>%I5\t%0,%1\;"
"bne\t%0,%z2,1f\;"
- "sc.<amo>.rl\t%6,%z3,%1\;"
+ "sc.<amo>%J5\t%6,%z3,%1\;"
"bnez\t%6,1b\;"
"1:";
}
@@ -440,9 +453,15 @@
emit_move_insn (shifted_o, gen_rtx_AND (SImode, shifted_o, mask));
emit_move_insn (shifted_n, gen_rtx_AND (SImode, shifted_n, mask));
+ enum memmodel model_success = (enum memmodel) INTVAL (operands[4]);
+ enum memmodel model_failure = (enum memmodel) INTVAL (operands[5]);
+ /* Find the union of the two memory models so we can satisfy both success
+ and failure memory models. */
+ rtx model = GEN_INT (riscv_union_memmodels (model_success, model_failure));
+
emit_insn (gen_subword_atomic_cas_strong (old, aligned_mem,
shifted_o, shifted_n,
- mask, not_mask));
+ model, mask, not_mask));
emit_move_insn (old, gen_rtx_ASHIFTRT (SImode, old,
gen_lowpart (QImode, shift)));
@@ -459,19 +478,20 @@
(unspec_volatile:SI [(match_operand:SI 2 "reg_or_0_operand" "rJ") ;; expected value
(match_operand:SI 3 "reg_or_0_operand" "rJ")] ;; desired value
UNSPEC_COMPARE_AND_SWAP_SUBWORD))
- (match_operand:SI 4 "register_operand" "rI") ;; mask
- (match_operand:SI 5 "register_operand" "rI") ;; not_mask
- (clobber (match_scratch:SI 6 "=&r"))] ;; tmp_1
+ (match_operand:SI 4 "const_int_operand") ;; model
+ (match_operand:SI 5 "register_operand" "rI") ;; mask
+ (match_operand:SI 6 "register_operand" "rI") ;; not_mask
+ (clobber (match_scratch:SI 7 "=&r"))] ;; tmp_1
"TARGET_ATOMIC && TARGET_INLINE_SUBWORD_ATOMIC"
{
return "1:\;"
- "lr.w.aqrl\t%0, %1\;"
- "and\t%6, %0, %4\;"
- "bne\t%6, %z2, 1f\;"
- "and\t%6, %0, %5\;"
- "or\t%6, %6, %3\;"
- "sc.w.rl\t%6, %6, %1\;"
- "bnez\t%6, 1b\;"
+ "lr.w%I4\t%0, %1\;"
+ "and\t%7, %0, %5\;"
+ "bne\t%7, %z2, 1f\;"
+ "and\t%7, %0, %6\;"
+ "or\t%7, %7, %3\;"
+ "sc.w%J4\t%7, %7, %1\;"
+ "bnez\t%7, 1b\;"
"1:";
}
[(set (attr "length") (const_int 28))])
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