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Re: Expanding roundeven (Was: Re: About GSOC.)


Hello.
I have made following changes to inspect inlining of roundeven with
the following test code:
double
plusone (double d)
{
    return __builtin_roundeven (d) + 1;
}

Running the program using -O2 foo.c gave internal compiler error which
I believe is because gcc_unreachable() at:

if (TARGET_SSE4_1)
    emit_insn (gen_sse4_1_round<mode>2
           (operands[0], operands[1], GEN_INT (ROUND_<ROUNDING>
                               | ROUND_NO_EXC)));
I think the following condition matches the criterion? :
> I think the code will be much clearer if it explicitly says
> ROUND_ROUNDEVEN | ROUND_NO_EXC,

     else if (TARGET_64BIT || (<MODE>mode != DFmode))
    {
      if (ROUND_<ROUNDING> == ROUND_FLOOR)
        ix86_expand_floorceil (operands[0], operands[1], true);
      else if (ROUND_<ROUNDING> == ROUND_CEIL)
        ix86_expand_floorceil (operands[0], operands[1], false);
      else if (ROUND_<ROUNDING> == ROUND_TRUNC)
        ix86_expand_trunc (operands[0], operands[1]);
      else
        gcc_unreachable ();
    }
in:
(define_expand "<rounding_insn><mode>2"
But with -mavx, generated the vroundsd insn. Does it mean ROUNDEVEN
should have a condition in the else if, but comments above
ix86_expand* functions in i386-expand.c says that those are for SSE2
sequences?

Thanks,
--Tejas


On Mon, 17 Jun 2019 at 22:45, Joseph Myers <joseph@codesourcery.com> wrote:
>
> On Mon, 17 Jun 2019, Tejas Joshi wrote:
>
> > > existing ROUND_NO_EXC definition in GCC.  A new definition will need
> > > adding alongside ROUND_FLOOR, ROUND_CEIL and ROUND_TRUNC to correspond to
> > > rounding to nearest with ties to even, evaluating to 0.)
> >
> > So (ROUND_ROUNDEVEN   0x0) be declared for rounding towards nearest
> > even for rounding mode argument? But reference says that RC field
> > should end up as 00B for rounding ties to even? I am also much
>
> I think the code will be much clearer if it explicitly says
> ROUND_ROUNDEVEN | ROUND_NO_EXC, than if it hardcodes implicit knowledge
> that 0 is the value used for rounding to nearest with ties to even.
>
> --
> Joseph S. Myers
> joseph@codesourcery.com
diff --git a/gcc/config/i386/i386-builtin.def b/gcc/config/i386/i386-builtin.def
index e547dda80f1..40536d7929c 100644
--- a/gcc/config/i386/i386-builtin.def
+++ b/gcc/config/i386/i386-builtin.def
@@ -906,6 +906,7 @@ BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundpd, "__builtin_ia32_floor
 BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundpd, "__builtin_ia32_ceilpd", IX86_BUILTIN_CEILPD, (enum rtx_code) ROUND_CEIL, (int) V2DF_FTYPE_V2DF_ROUND)
 BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundpd, "__builtin_ia32_truncpd", IX86_BUILTIN_TRUNCPD, (enum rtx_code) ROUND_TRUNC, (int) V2DF_FTYPE_V2DF_ROUND)
 BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundpd, "__builtin_ia32_rintpd", IX86_BUILTIN_RINTPD, (enum rtx_code) ROUND_MXCSR, (int) V2DF_FTYPE_V2DF_ROUND)
+BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundpd, "__builtin_ia32_roundevenpd", IX86_BUILTIN_ROUNDEVENPD, (enum rtx_code) ROUND_ROUNDEVEN, (int) V2DF_FTYPE_V2DF_ROUND)
 
 BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundpd_vec_pack_sfix, "__builtin_ia32_floorpd_vec_pack_sfix", IX86_BUILTIN_FLOORPD_VEC_PACK_SFIX, (enum rtx_code) ROUND_FLOOR, (int) V4SI_FTYPE_V2DF_V2DF_ROUND)
 BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundpd_vec_pack_sfix, "__builtin_ia32_ceilpd_vec_pack_sfix", IX86_BUILTIN_CEILPD_VEC_PACK_SFIX, (enum rtx_code) ROUND_CEIL, (int) V4SI_FTYPE_V2DF_V2DF_ROUND)
@@ -917,6 +918,7 @@ BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundps, "__builtin_ia32_floor
 BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundps, "__builtin_ia32_ceilps", IX86_BUILTIN_CEILPS, (enum rtx_code) ROUND_CEIL, (int) V4SF_FTYPE_V4SF_ROUND)
 BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundps, "__builtin_ia32_truncps", IX86_BUILTIN_TRUNCPS, (enum rtx_code) ROUND_TRUNC, (int) V4SF_FTYPE_V4SF_ROUND)
 BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundps, "__builtin_ia32_rintps", IX86_BUILTIN_RINTPS, (enum rtx_code) ROUND_MXCSR, (int) V4SF_FTYPE_V4SF_ROUND)
+BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundps, "__builtin_ia32_roundevenps", IX86_BUILTIN_ROUNDEVENPS, (enum rtx_code) ROUND_ROUNDEVEN, (int) V4SF_FTYPE_V4SF_ROUND)
 
 BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundps_sfix, "__builtin_ia32_floorps_sfix", IX86_BUILTIN_FLOORPS_SFIX, (enum rtx_code) ROUND_FLOOR, (int) V4SI_FTYPE_V4SF_ROUND)
 BDESC (OPTION_MASK_ISA_SSE4_1, 0, CODE_FOR_sse4_1_roundps_sfix, "__builtin_ia32_ceilps_sfix", IX86_BUILTIN_CEILPS_SFIX, (enum rtx_code) ROUND_CEIL, (int) V4SI_FTYPE_V4SF_ROUND)
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index 01213ccb82c..ce58b5e5c28 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -2468,6 +2468,7 @@ enum ix86_stack_slot
   SLOT_CW_TRUNC,
   SLOT_CW_FLOOR,
   SLOT_CW_CEIL,
+  SLOT_CW_ROUNDEVEN,
   SLOT_STV_TEMP,
   MAX_386_STACK_LOCALS
 };
@@ -2479,6 +2480,7 @@ enum ix86_entity
   I387_TRUNC,
   I387_FLOOR,
   I387_CEIL,
+  I387_ROUNDEVEN,
   MAX_386_ENTITIES
 };
 
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 01338e294ab..b11af2f4308 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -144,6 +144,7 @@
   UNSPEC_FRNDINT_FLOOR
   UNSPEC_FRNDINT_CEIL
   UNSPEC_FRNDINT_TRUNC
+  UNSPEC_FRNDINT_ROUNDEVEN
   UNSPEC_FIST_FLOOR
   UNSPEC_FIST_CEIL
 
@@ -303,7 +304,8 @@
 
 ;; Constants to represent rounding modes in the ROUND instruction
 (define_constants
-  [(ROUND_FLOOR			0x1)
+  [(ROUND_ROUNDEVEN		0x0)
+   (ROUND_FLOOR			0x1)
    (ROUND_CEIL			0x2)
    (ROUND_TRUNC			0x3)
    (ROUND_MXCSR			0x4)
@@ -779,7 +781,7 @@
 
 ;; Defines rounding mode of an FP operation.
 
-(define_attr "i387_cw" "trunc,floor,ceil,uninitialized,any"
+(define_attr "i387_cw" "trunc,floor,ceil,roundeven,uninitialized,any"
   (const_string "any"))
 
 ;; Define attribute to indicate AVX insns with partial XMM register update.
@@ -16254,7 +16256,8 @@
 (define_int_iterator FRNDINT_ROUNDING
 	[UNSPEC_FRNDINT_FLOOR
 	 UNSPEC_FRNDINT_CEIL
-	 UNSPEC_FRNDINT_TRUNC])
+	 UNSPEC_FRNDINT_TRUNC
+   UNSPEC_FRNDINT_ROUNDEVEN])
 
 (define_int_iterator FIST_ROUNDING
 	[UNSPEC_FIST_FLOOR
@@ -16265,6 +16268,7 @@
 	[(UNSPEC_FRNDINT_FLOOR "floor")
 	 (UNSPEC_FRNDINT_CEIL "ceil")
 	 (UNSPEC_FRNDINT_TRUNC "btrunc")
+   (UNSPEC_FRNDINT_ROUNDEVEN "roundeven")
 	 (UNSPEC_FIST_FLOOR "floor")
 	 (UNSPEC_FIST_CEIL "ceil")])
 
@@ -16272,6 +16276,7 @@
 	[(UNSPEC_FRNDINT_FLOOR "floor")
 	 (UNSPEC_FRNDINT_CEIL "ceil")
 	 (UNSPEC_FRNDINT_TRUNC "trunc")
+   (UNSPEC_FRNDINT_ROUNDEVEN "roundeven")
 	 (UNSPEC_FIST_FLOOR "floor")
 	 (UNSPEC_FIST_CEIL "ceil")])
 
@@ -16279,6 +16284,7 @@
 	[(UNSPEC_FRNDINT_FLOOR "FLOOR")
 	 (UNSPEC_FRNDINT_CEIL "CEIL")
 	 (UNSPEC_FRNDINT_TRUNC "TRUNC")
+   (UNSPEC_FRNDINT_ROUNDEVEN "ROUNDEVEN")
 	 (UNSPEC_FIST_FLOOR "FLOOR")
 	 (UNSPEC_FIST_CEIL "CEIL")])
 
diff --git a/gcc/internal-fn.def b/gcc/internal-fn.def
index 016301a58d8..c07d48594e3 100644
--- a/gcc/internal-fn.def
+++ b/gcc/internal-fn.def
@@ -231,6 +231,7 @@ DEF_INTERNAL_FLT_FLOATN_FN (FLOOR, ECF_CONST, floor, unary)
 DEF_INTERNAL_FLT_FLOATN_FN (NEARBYINT, ECF_CONST, nearbyint, unary)
 DEF_INTERNAL_FLT_FLOATN_FN (RINT, ECF_CONST, rint, unary)
 DEF_INTERNAL_FLT_FLOATN_FN (ROUND, ECF_CONST, round, unary)
+DEF_INTERNAL_FLT_FLOATN_FN (ROUNDEVEN, ECF_CONST, roundeven, unary)
 DEF_INTERNAL_FLT_FLOATN_FN (TRUNC, ECF_CONST, btrunc, unary)
 
 /* Binary math functions.  */
diff --git a/gcc/optabs.def b/gcc/optabs.def
index 8af3a2f43fd..839d250b8c6 100644
--- a/gcc/optabs.def
+++ b/gcc/optabs.def
@@ -267,6 +267,7 @@ OPTAB_D (fnms_optab, "fnms$a4")
 
 OPTAB_D (rint_optab, "rint$a2")
 OPTAB_D (round_optab, "round$a2")
+OPTAB_D (roundeven_optab, "roundeven$a2")
 OPTAB_D (floor_optab, "floor$a2")
 OPTAB_D (ceil_optab, "ceil$a2")
 OPTAB_D (btrunc_optab, "btrunc$a2")

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