Implement -ffp-contract=on for C and C++ without changing default
behavior (=off for -std=cNN, =fast for C++ and -std=gnuNN).
gcc/c-family/ChangeLog:
* c-gimplify.cc (fma_supported_p): New helper.
(c_gimplify_expr) [PLUS_EXPR, MINUS_EXPR]: Implement FMA
contraction.
gcc/ChangeLog:
* common.opt (fp_contract_mode) [on]: Remove fallback.
* config/sh/sh.md (*fmasf4): Correct flag_fp_contract_mode test.
* doc/invoke.texi (-ffp-contract): Update.
* trans-mem.cc (diagnose_tm_1): Skip internal function calls.
---
gcc/c-family/c-gimplify.cc | 78 ++++++++++++++++++++++++++++++++++++++
gcc/common.opt | 3 +-
gcc/config/sh/sh.md | 2 +-
gcc/doc/invoke.texi | 8 ++--
gcc/trans-mem.cc | 3 ++
5 files changed, 88 insertions(+), 6 deletions(-)
diff --git a/gcc/c-family/c-gimplify.cc b/gcc/c-family/c-gimplify.cc
index ef5c7d919f..f7635d3b0c 100644
--- a/gcc/c-family/c-gimplify.cc
+++ b/gcc/c-family/c-gimplify.cc
@@ -41,6 +41,8 @@ along with GCC; see the file COPYING3. If not see
#include "c-ubsan.h"
#include "tree-nested.h"
#include "context.h"
+#include "tree-pass.h"
+#include "internal-fn.h"
/* The gimplification pass converts the language-dependent trees
(ld-trees) emitted by the parser into language-independent trees
@@ -686,6 +688,14 @@ c_build_bind_expr (location_t loc, tree block, tree body)
return bind;
}
+/* Helper for c_gimplify_expr: test if target supports fma-like FN. */
+
+static bool
+fma_supported_p (enum internal_fn fn, tree type)
+{
+ return direct_internal_fn_supported_p (fn, type, OPTIMIZE_FOR_BOTH);
+}
+
/* Gimplification of expression trees. */
/* Do C-specific gimplification on *EXPR_P. PRE_P and POST_P are as in
@@ -739,6 +749,74 @@ c_gimplify_expr (tree *expr_p, gimple_seq *pre_p
ATTRIBUTE_UNUSED,
break;
}
+ case PLUS_EXPR:
+ case MINUS_EXPR:
+ {
+ tree type = TREE_TYPE (*expr_p);
+ /* For -ffp-contract=on we need to attempt FMA contraction only
+ during initial gimplification. Late contraction across statement
+ boundaries would violate language semantics. */
+ if (SCALAR_FLOAT_TYPE_P (type)
+ && flag_fp_contract_mode == FP_CONTRACT_ON
+ && cfun && !(cfun->curr_properties & PROP_gimple_any)
+ && fma_supported_p (IFN_FMA, type))
+ {
+ bool neg_mul = false, neg_add = code == MINUS_EXPR;
+
+ tree *op0_p = &TREE_OPERAND (*expr_p, 0);
+ tree *op1_p = &TREE_OPERAND (*expr_p, 1);
+
+ /* Look for ±(x * y) ± z, swapping operands if necessary. */
+ if (TREE_CODE (*op0_p) == NEGATE_EXPR
+ && TREE_CODE (TREE_OPERAND (*op0_p, 0)) == MULT_EXPR)
+ /* '*EXPR_P' is '-(x * y) ± z'. This is fine. */;
+ else if (TREE_CODE (*op0_p) != MULT_EXPR)
+ {
+ std::swap (op0_p, op1_p);
+ std::swap (neg_mul, neg_add);
+ }
+ if (TREE_CODE (*op0_p) == NEGATE_EXPR)
+ {
+ op0_p = &TREE_OPERAND (*op0_p, 0);
+ neg_mul = !neg_mul;
+ }
+ if (TREE_CODE (*op0_p) != MULT_EXPR)
+ break;
+ auto_vec<tree, 3> ops (3);
+ ops.quick_push (TREE_OPERAND (*op0_p, 0));
+ ops.quick_push (TREE_OPERAND (*op0_p, 1));
+ ops.quick_push (*op1_p);
+
+ enum internal_fn ifn = IFN_FMA;
+ if (neg_mul)
+ {
+ if (fma_supported_p (IFN_FNMA, type))
+ ifn = IFN_FNMA;
+ else
+ ops[0] = build1 (NEGATE_EXPR, type, ops[0]);
+ }
+ if (neg_add)
+ {
+ enum internal_fn ifn2 = ifn == IFN_FMA ? IFN_FMS : IFN_FNMS;
+ if (fma_supported_p (ifn2, type))
+ ifn = ifn2;
+ else
+ ops[2] = build1 (NEGATE_EXPR, type, ops[2]);
+ }
+ for (auto &&op : ops)
+ if (gimplify_expr (&op, pre_p, post_p, is_gimple_val, fb_rvalue)
+ == GS_ERROR)
+ return GS_ERROR;
+
+ gcall *call = gimple_build_call_internal_vec (ifn, ops);
+ gimple_seq_add_stmt_without_update (pre_p, call);
+ *expr_p = create_tmp_var (type);
+ gimple_call_set_lhs (call, *expr_p);
+ return GS_ALL_DONE;
+ }
+ break;
+ }
+
default:;
}
diff --git a/gcc/common.opt b/gcc/common.opt
index a28ca13385..3daec85aef 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1662,9 +1662,8 @@ Name(fp_contract_mode) Type(enum fp_contract_mode)
UnknownError(unknown floating
EnumValue
Enum(fp_contract_mode) String(off) Value(FP_CONTRACT_OFF)
-; Not implemented, fall back to conservative FP_CONTRACT_OFF.
EnumValue
-Enum(fp_contract_mode) String(on) Value(FP_CONTRACT_OFF)
+Enum(fp_contract_mode) String(on) Value(FP_CONTRACT_ON)
EnumValue
Enum(fp_contract_mode) String(fast) Value(FP_CONTRACT_FAST)
diff --git a/gcc/config/sh/sh.md b/gcc/config/sh/sh.md
index 4622dba012..5cb1795482 100644
--- a/gcc/config/sh/sh.md
+++ b/gcc/config/sh/sh.md
@@ -9269,7 +9269,7 @@ (define_insn_and_split "*fmasf4"
(match_operand:SF 3 "arith_reg_operand" "0")))
(clobber (reg:SI FPSCR_STAT_REG))
(use (reg:SI FPSCR_MODES_REG))]
- "TARGET_SH2E && flag_fp_contract_mode != FP_CONTRACT_OFF"
+ "TARGET_SH2E && flag_fp_contract_mode == FP_CONTRACT_FAST"
"fmac %1,%2,%0"
"&& can_create_pseudo_p ()"
[(parallel [(set (match_dup 0)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index b92b857602..cb1e9a1d9f 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -11983,10 +11983,12 @@ This option is enabled by default at optimization
levels @option{-O1},
such as forming of fused multiply-add operations if the target has
native support for them.
@option{-ffp-contract=on} enables floating-point expression contraction
-if allowed by the language standard. This is currently not implemented
-and treated equal to @option{-ffp-contract=off}.
+if allowed by the language standard. This is implemented for C and C++,
+where it enables contraction within one expression, but not across
+different statements.
-The default is @option{-ffp-contract=fast}.
+The default is @option{-ffp-contract=off} for C in a standards compliant mode
+(@option{-std=c11} or similar), @option{-ffp-contract=fast} otherwise.
@opindex fomit-frame-pointer
@item -fomit-frame-pointer
diff --git a/gcc/trans-mem.cc b/gcc/trans-mem.cc
index 4b129663e0..2174faef4c 100644
--- a/gcc/trans-mem.cc
+++ b/gcc/trans-mem.cc
@@ -637,6 +637,9 @@ diagnose_tm_1 (gimple_stmt_iterator *gsi, bool
*handled_ops_p,
{
case GIMPLE_CALL:
{
+ if (gimple_call_internal_p (stmt))
+ break;
+
tree fn = gimple_call_fn (stmt);
if ((d->summary_flags & DIAG_TM_OUTER) == 0
--
2.39.2
