[gcc r10-10116] rs6000: Expand fmod and remainder when built with fast-math [PR97142]

[Xiong Hu Luo <luoxhu@gcc.gnu.org>]

https://gcc.gnu.org/g:68d525ee859041b21d87b23030d1e829a9cc3b6f

commit r10-10116-g68d525ee859041b21d87b23030d1e829a9cc3b6f
Author: Xionghu Luo <luoxhu@linux.ibm.com>
Date:   Mon Sep 6 20:22:50 2021 -0500

    rs6000: Expand fmod and remainder when built with fast-math [PR97142]
    
    fmod/fmodf and remainder/remainderf could be expanded instead of library
    call when fast-math build, which is much faster.
    
    fmodf:
         fdivs   f0,f1,f2
         friz    f0,f0
         fnmsubs f1,f2,f0,f1
    
    remainderf:
         fdivs   f0,f1,f2
         frin    f0,f0
         fnmsubs f1,f2,f0,f1
    
    SPEC2017 Ofast P8LE: 511.povray_r +1.14%,  526.blender_r +1.72%
    
    gcc/ChangeLog:
    
    2021-09-07  Xionghu Luo  <luoxhu@linux.ibm.com>
    
            PR target/97142
            * config/rs6000/rs6000.md (fmod<mode>3): New define_expand.
            (remainder<mode>3): Likewise.
    
    gcc/testsuite/ChangeLog:
    
    2021-09-07  Xionghu Luo  <luoxhu@linux.ibm.com>
    
            PR target/97142
            * gcc.target/powerpc/pr97142.c: New test.
    
    (cherry picked from commit 546ecb0054af302acf0839c7f3eb78598f8c0672)

Diff:
---
 gcc/config/rs6000/rs6000.md                | 36 ++++++++++++++++++++++++++++++
 gcc/testsuite/gcc.target/powerpc/pr97142.c | 35 +++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index c4d7cdb6fa7..61a14fb5b9f 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -4806,6 +4806,42 @@
   [(set_attr "type" "fp")
    (set_attr "isa" "*,<Fisa>")])
 
+(define_expand "fmod<mode>3"
+  [(use (match_operand:SFDF 0 "gpc_reg_operand"))
+	(use (match_operand:SFDF 1 "gpc_reg_operand"))
+	(use (match_operand:SFDF 2 "gpc_reg_operand"))]
+  "TARGET_HARD_FLOAT
+   && TARGET_FPRND
+   && flag_unsafe_math_optimizations"
+{
+  rtx div = gen_reg_rtx (<MODE>mode);
+  emit_insn (gen_div<mode>3 (div, operands[1], operands[2]));
+
+  rtx friz = gen_reg_rtx (<MODE>mode);
+  emit_insn (gen_btrunc<mode>2 (friz, div));
+
+  emit_insn (gen_nfms<mode>4 (operands[0], operands[2], friz, operands[1]));
+  DONE;
+ })
+
+(define_expand "remainder<mode>3"
+  [(use (match_operand:SFDF 0 "gpc_reg_operand"))
+	(use (match_operand:SFDF 1 "gpc_reg_operand"))
+	(use (match_operand:SFDF 2 "gpc_reg_operand"))]
+  "TARGET_HARD_FLOAT
+   && TARGET_FPRND
+   && flag_unsafe_math_optimizations"
+{
+  rtx div = gen_reg_rtx (<MODE>mode);
+  emit_insn (gen_div<mode>3 (div, operands[1], operands[2]));
+
+  rtx frin = gen_reg_rtx (<MODE>mode);
+  emit_insn (gen_round<mode>2 (frin, div));
+
+  emit_insn (gen_nfms<mode>4 (operands[0], operands[2], frin, operands[1]));
+  DONE;
+ })
+
 (define_insn "*rsqrt<mode>2"
   [(set (match_operand:SFDF 0 "gpc_reg_operand" "=<Ff>,wa")
 	(unspec:SFDF [(match_operand:SFDF 1 "gpc_reg_operand" "<Ff>,wa")]
diff --git a/gcc/testsuite/gcc.target/powerpc/pr97142.c b/gcc/testsuite/gcc.target/powerpc/pr97142.c
new file mode 100644
index 00000000000..0e5f1c1f61b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr97142.c
@@ -0,0 +1,35 @@
+/* { dg-do compile } */
+/* { dg-options "-Ofast" } */
+
+#include <math.h>
+
+float test1 (float x, float y)
+{
+  return fmodf (x, y);
+}
+
+double test2 (double x, double y)
+{
+  return fmod (x, y);
+}
+
+float test3 (float x, float y)
+{
+  return remainderf (x, y);
+}
+
+double test4 (double x, double y)
+{
+  return remainder (x, y);
+}
+
+/* { dg-final { scan-assembler-not {(?n)\mb.*fmod} } } */
+/* { dg-final { scan-assembler-not {(?n)\mb.*fmodf} } } */
+/* { dg-final { scan-assembler-not {(?n)\mb.*remainder} } } */
+/* { dg-final { scan-assembler-not {(?n)\mb.*remainderf} } } */
+/* { dg-final { scan-assembler-times {\mfdiv\M} 2 } } */
+/* { dg-final { scan-assembler-times {\mfdivs\M} 2 } } */
+/* { dg-final { scan-assembler-times {\mfnmsub\M} 2 } } */
+/* { dg-final { scan-assembler-times {\mfnmsubs\M} 2 } } */
+/* { dg-final { scan-assembler-times {\mfriz\M} 2 } } */
+/* { dg-final { scan-assembler-times {\mfrin\M} 2 } } */