Re: [PATCH v2 4/4] LoongArch: Add flogb.{s, d} instructions and expand logb{sf,df}2

[Lulu Cheng]

LGTM!

Thanks.

在 2022/11/9 下午9:53, Xi Ruoyao 写道:

On LoongArch, flogb instructions extract the exponent of a non-negative
floating point value, but produces NaN for negative values.  So we need
to add a fabs instruction when we expand logb.

gcc/ChangeLog:

        * config/loongarch/loongarch.md (UNSPEC_FLOGB): New unspec.
        (type): Add flogb.
        (logb_non_negative<mode>2): New instruction template.
        (logb<mode>2): New define_expand.

gcc/testsuite/ChangeLog:

        * gcc.target/loongarch/flogb.c: New test.
---
  gcc/config/loongarch/loongarch.md          | 35 ++++++++++++++++++++--
  gcc/testsuite/gcc.target/loongarch/flogb.c | 18 +++++++++++
  2 files changed, 51 insertions(+), 2 deletions(-)
  create mode 100644 gcc/testsuite/gcc.target/loongarch/flogb.c

diff --git a/gcc/config/loongarch/loongarch.md 
b/gcc/config/loongarch/loongarch.md
index c141c9adde2..682ab961741 100644
--- a/gcc/config/loongarch/loongarch.md
+++ b/gcc/config/loongarch/loongarch.md
@@ -42,6 +42,7 @@ (define_c_enum "unspec" [
    UNSPEC_FTINTRM
    UNSPEC_FTINTRP
    UNSPEC_FSCALEB
+  UNSPEC_FLOGB

;; Override return address for exception handling.

    UNSPEC_EH_RETURN
@@ -217,6 +218,7 @@ (define_attr "qword_mode" "no,yes"
  ;; fdiv               floating point divide
  ;; frdiv      floating point reciprocal divide
  ;; fabs               floating point absolute value
+;; flogb       floating point exponent extract
  ;; fneg               floating point negation
  ;; fcmp               floating point compare
  ;; fcopysign  floating point copysign
@@ -233,8 +235,8 @@ (define_attr "type"
    "unknown,branch,jump,call,load,fpload,fpidxload,store,fpstore,fpidxstore,
     prefetch,prefetchx,condmove,mgtf,mftg,const,arith,logical,
     shift,slt,signext,clz,trap,imul,idiv,move,
-   fmove,fadd,fmul,fmadd,fdiv,frdiv,fabs,fneg,fcmp,fcopysign,fcvt,fscaleb,
-   fsqrt,frsqrt,accext,accmod,multi,atomic,syncloop,nop,ghost"
+   fmove,fadd,fmul,fmadd,fdiv,frdiv,fabs,flogb,fneg,fcmp,fcopysign,fcvt,
+   fscaleb,fsqrt,frsqrt,accext,accmod,multi,atomic,syncloop,nop,ghost"
    (cond [(eq_attr "jirl" "!unset") (const_string "call")
         (eq_attr "got" "load") (const_string "load")

@@ -1039,6 +1041,35 @@ (define_insn "ldexp<mode>3"

     (set_attr "mode" "<UNITMODE>")])
  
  ;;
+;;  ....................
+;;
+;;     FLOATING POINT EXPONENT EXTRACT
+;;
+;;  ....................
+
+(define_insn "logb_non_negative<mode>2"
+  [(set (match_operand:ANYF 0 "register_operand" "=f")
+       (unspec:ANYF [(match_operand:ANYF 1 "register_operand" "f")]
+                    UNSPEC_FLOGB))]
+  "TARGET_HARD_FLOAT"
+  "flogb.<fmt>\t%0,%1"
+  [(set_attr "type" "flogb")
+   (set_attr "mode" "<UNITMODE>")])
+
+(define_expand "logb<mode>2"
+  [(set (match_operand:ANYF 0 "register_operand")
+       (unspec:ANYF [(abs:ANYF (match_operand:ANYF 1 "register_operand"))]
+                    UNSPEC_FLOGB))]
+  "TARGET_HARD_FLOAT"
+{
+  rtx tmp = gen_reg_rtx (<MODE>mode);
+
+  emit_insn (gen_abs<mode>2 (tmp, operands[1]));
+  emit_insn (gen_logb_non_negative<mode>2 (operands[0], tmp));
+  DONE;
+})
+
+;;
  ;;  ...................
  ;;
  ;;  Count leading zeroes.
diff --git a/gcc/testsuite/gcc.target/loongarch/flogb.c 
b/gcc/testsuite/gcc.target/loongarch/flogb.c
new file mode 100644
index 00000000000..1daefe54e13
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/flogb.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-mdouble-float -fno-math-errno" } */
+/* { dg-final { scan-assembler "fabs\\.s" } } */
+/* { dg-final { scan-assembler "fabs\\.d" } } */
+/* { dg-final { scan-assembler "flogb\\.s" } } */
+/* { dg-final { scan-assembler "flogb\\.d" } } */
+
+double
+my_logb (double a)
+{
+  return __builtin_logb (a);
+}
+
+float
+my_logbf (float a)
+{
+  return __builtin_logbf (a);
+}