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[COMMITTED] RISC-V: use fclass insns to implement isfinite, isnormal and isinf builtins

Message ID 20240815211105.1072463-1-vineetg@rivosinc.com
State New
Headers show
Series [COMMITTED] RISC-V: use fclass insns to implement isfinite, isnormal and isinf builtins | expand

Commit Message

Vineet Gupta Aug. 15, 2024, 9:11 p.m. UTC 
Currently these builtins use float compare instructions which require
FP flags to be saved/restored which could be costly in uarch.
RV Base ISA already has FCLASS.{d,s,h} instruction to compare/identify FP
values w/o disturbing FP exception flags.

Now that upstream supports the corresponding optabs, wire them up in the
backend.

gcc/ChangeLog:
	* config/riscv/riscv.md: define_insn for fclass insn.
	define_expand for isfinite, isnormal, isinf.

gcc/testsuite/ChangeLog:
	* gcc.target/riscv/fclass.c: New tests.

Tested-by: Edwin Lu <ewlu@rivosinc.com> # pre-commit-CI #2060
Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>
---
 gcc/config/riscv/riscv.md               | 63 +++++++++++++++++++++++++
 gcc/testsuite/gcc.target/riscv/fclass.c | 38 +++++++++++++++
 2 files changed, 101 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/riscv/fclass.c
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Patch

diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index 5e3ef789e42e..f8d8162c0f91 100644
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -68,6 +68,7 @@ 
   UNSPEC_FMAX
   UNSPEC_FMINM
   UNSPEC_FMAXM
+  UNSPEC_FCLASS
 
   ;; Stack tie
   UNSPEC_TIE
@@ -3478,6 +3479,68 @@ 
    (set_attr "mode" "<UNITMODE>")
    (set (attr "length") (const_int 16))])
 
+;; fclass instruction output bitmap
+;;   0 negative infinity
+;;   1 negative normal number.
+;;   2 negative subnormal number.
+;;   3 -0
+;;   4 +0
+;;   5 positive subnormal number.
+;;   6 positive normal number.
+;;   7 positive infinity
+;;   8 signaling NaN.
+;;   9 quiet NaN
+
+(define_insn "fclass<ANYF:mode><X:mode>"
+  [(set (match_operand:X	     0 "register_operand" "=r")
+	(unspec [(match_operand:ANYF 1 "register_operand" " f")]
+		   UNSPEC_FCLASS))]
+  "TARGET_HARD_FLOAT"
+  "fclass.<fmt>\t%0,%1";
+  [(set_attr "type" "fcmp")
+   (set_attr "mode" "<UNITMODE>")])
+
+;; Implements optab for isfinite, isnormal, isinf
+
+(define_int_iterator FCLASS_MASK [126 66 129])
+(define_int_attr fclass_optab
+  [(126	"isfinite")
+   (66	"isnormal")
+   (129	"isinf")])
+
+(define_expand "<FCLASS_MASK:fclass_optab><ANYF:mode>2"
+  [(match_operand      0 "register_operand" "=r")
+   (match_operand:ANYF 1 "register_operand" " f")
+   (const_int FCLASS_MASK)]
+  "TARGET_HARD_FLOAT"
+{
+  if (GET_MODE (operands[0]) != SImode
+      && GET_MODE (operands[0]) != word_mode)
+    FAIL;
+
+  rtx t = gen_reg_rtx (word_mode);
+  rtx t_op0 = gen_reg_rtx (word_mode);
+
+  if (TARGET_64BIT)
+    emit_insn (gen_fclass<ANYF:mode>di (t, operands[1]));
+  else
+    emit_insn (gen_fclass<ANYF:mode>si (t, operands[1]));
+
+  riscv_emit_binary (AND, t, t, GEN_INT (<FCLASS_MASK>));
+  rtx cmp = gen_rtx_NE (word_mode, t, const0_rtx);
+  emit_insn (gen_cstore<mode>4 (t_op0, cmp, t, const0_rtx));
+
+  if (TARGET_64BIT)
+    {
+      t_op0 = gen_lowpart (SImode, t_op0);
+      SUBREG_PROMOTED_VAR_P (t_op0) = 1;
+      SUBREG_PROMOTED_SET (t_op0, SRP_SIGNED);
+    }
+
+  emit_move_insn (operands[0], t_op0);
+  DONE;
+})
+
 (define_insn "*seq_zero_<X:mode><GPR:mode>"
   [(set (match_operand:GPR       0 "register_operand" "=r")
 	(eq:GPR (match_operand:X 1 "register_operand" " r")
diff --git a/gcc/testsuite/gcc.target/riscv/fclass.c b/gcc/testsuite/gcc.target/riscv/fclass.c
new file mode 100644
index 000000000000..ea0f173ecf4b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/fclass.c
@@ -0,0 +1,38 @@ 
+/* { dg-do compile } */
+/* { dg-require-effective-target hard_float } */
+/* { dg-options "-march=rv64gc -mabi=lp64d  -ftrapping-math" { target { rv64 } } } */
+/* { dg-options "-march=rv32gc -mabi=ilp32d -ftrapping-math" { target { rv32 } } } */
+
+int d_isfinite(double a)
+{
+  return __builtin_isfinite(a);
+}
+
+int d_isnormal(double a)
+{
+  return __builtin_isnormal(a);
+}
+
+int d_isinf(double a)
+{
+  return __builtin_isinf(a);
+}
+
+int f_isfinite(float a)
+{
+  return __builtin_isfinite(a);
+}
+
+int f_isnormal(float a)
+{
+  return __builtin_isnormal(a);
+}
+
+int f_isinf(float a)
+{
+  return __builtin_isinf(a);
+}
+
+/* { dg-final { scan-assembler-not   {\mfrflags}  } } */
+/* { dg-final { scan-assembler-not   {\mfsflags}  } } */
+/* { dg-final { scan-assembler-times {\tfclass} 6 } } */