Re: [PATCH][GCC][AArch64] optimize float immediate moves (2 /4) - HF/DF/SF mode.

[Tamar Christina <Tamar.Christina@arm.com>]

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Hi all,

Here's the re-spun patch.
Aside from the grouping of the split patterns it now also uses h register for the fmov for HF when available,
otherwise it forces a literal load.

Regression tested on aarch64-none-linux-gnu and no regressions.

OK for trunk?

Thanks,
Tamar


gcc/
2017-06-26  Tamar Christina  <tamar.christina@arm.com>
            Richard Sandiford <richard.sandiford@linaro.org>

        * config/aarch64/aarch64.md (mov<mode>): Generalize.
        (*movhf_aarch64, *movsf_aarch64, *movdf_aarch64):
        Add integer and movi cases.
        (movi-split-hf-df-sf split, fp16): New.
        (enabled): Added TARGET_FP_F16INST.
        * config/aarch64/iterators.md (GPF_HF): New.
________________________________________
From: Tamar Christina
Sent: Wednesday, June 21, 2017 11:48:33 AM
To: James Greenhalgh
Cc: GCC Patches; nd; Marcus Shawcroft; Richard Earnshaw
Subject: RE: [PATCH][GCC][AArch64] optimize float immediate moves (2 /4) - HF/DF/SF mode.

> >     movi\\t%0.4h, #0
> > -   mov\\t%0.h[0], %w1
> > +   fmov\\t%s0, %w1
>
> Should this not be %h0?

The problem is that H registers are only available in ARMv8.2+,
I'm not sure what to do about ARMv8.1 given your other feedback
Pointing out that the bit patterns between how it's stored in s vs h registers
differ.

>
> >     umov\\t%w0, %1.h[0]
> >     mov\\t%0.h[0], %1.h[0]
> > +   fmov\\t%s0, %1
>
> Likewise, and much more important for correctness as it changes the way the
> bit pattern ends up in the register (see table C2-1 in release B.a of the ARM
> Architecture Reference Manual for ARMv8-A), here.
>
> > +   * return aarch64_output_scalar_simd_mov_immediate (operands[1],
> > + SImode);
> >     ldr\\t%h0, %1
> >     str\\t%h1, %0
> >     ldrh\\t%w0, %1
> >     strh\\t%w1, %0
> >     mov\\t%w0, %w1"
> > -  [(set_attr "type"
> "neon_move,neon_from_gp,neon_to_gp,neon_move,\
> > -                     f_loads,f_stores,load1,store1,mov_reg")
> > -   (set_attr "simd" "yes,yes,yes,yes,*,*,*,*,*")]
> > +  "&& can_create_pseudo_p ()
> > +   && !aarch64_can_const_movi_rtx_p (operands[1], HFmode)
> > +   && !aarch64_float_const_representable_p (operands[1])
> > +   &&  aarch64_float_const_rtx_p (operands[1])"
> > +  [(const_int 0)]
> > +  "{
> > +    unsigned HOST_WIDE_INT ival;
> > +    if (!aarch64_reinterpret_float_as_int (operands[1], &ival))
> > +      FAIL;
> > +
> > +    rtx tmp = gen_reg_rtx (SImode);
> > +    aarch64_expand_mov_immediate (tmp, GEN_INT (ival));
> > +    tmp = simplify_gen_subreg (HImode, tmp, SImode, 0);
> > +    emit_move_insn (operands[0], gen_lowpart (HFmode, tmp));
> > +    DONE;
> > +  }"
> > +  [(set_attr "type" "neon_move,f_mcr,neon_to_gp,neon_move,fconsts,
> \
> > +                neon_move,f_loads,f_stores,load1,store1,mov_reg")
> > +   (set_attr "simd" "yes,*,yes,yes,*,yes,*,*,*,*,*")]
> >  )
>
> Thanks,
> James


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diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 1a721bfbe42270ec75268b6e2366290aa6ad2134..c951efc383c17ea81800e482e39760eb17830c0a 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -181,6 +181,11 @@
 ;; will be disabled when !TARGET_FLOAT.
 (define_attr "fp" "no,yes" (const_string "no"))
 
+;; Attribute that specifies whether or not the instruction touches half
+;; precision fp registers.  When this is set to yes for an alternative,
+;; that alternative will be disabled when !TARGET_FP_F16INST.
+(define_attr "fp16" "no,yes" (const_string "no"))
+
 ;; Attribute that specifies whether or not the instruction touches simd
 ;; registers.  When this is set to yes for an alternative, that alternative
 ;; will be disabled when !TARGET_SIMD.
@@ -194,11 +199,14 @@
 ;; registers when -mgeneral-regs-only is specified.
 (define_attr "enabled" "no,yes"
   (cond [(ior
-	(and (eq_attr "fp" "yes")
-	     (eq (symbol_ref "TARGET_FLOAT") (const_int 0)))
-	(and (eq_attr "simd" "yes")
-	     (eq (symbol_ref "TARGET_SIMD") (const_int 0))))
-	     (const_string "no")
+	    (ior
+		(and (eq_attr "fp" "yes")
+		     (eq (symbol_ref "TARGET_FLOAT") (const_int 0)))
+		(and (eq_attr "simd" "yes")
+		     (eq (symbol_ref "TARGET_SIMD") (const_int 0))))
+	    (and (eq_attr "fp16" "yes")
+		 (eq (symbol_ref "TARGET_FP_F16INST") (const_int 0))))
+	    (const_string "no")
 	] (const_string "yes")))
 
 ;; Attribute that specifies whether we are dealing with a branch to a
@@ -1062,65 +1070,94 @@
 )
 
 (define_insn "*movhf_aarch64"
-  [(set (match_operand:HF 0 "nonimmediate_operand" "=w,w  ,?r,w,w,m,r,m ,r")
-	(match_operand:HF 1 "general_operand"      "Y ,?rY, w,w,m,w,m,rY,r"))]
+  [(set (match_operand:HF 0 "nonimmediate_operand" "=w,w  ,?r,w,w  ,w  ,w,m,r,m ,r")
+	(match_operand:HF 1 "general_operand"      "Y ,?rY, w,w,Ufc,Uvi,m,w,m,rY,r"))]
   "TARGET_FLOAT && (register_operand (operands[0], HFmode)
-    || aarch64_reg_or_fp_zero (operands[1], HFmode))"
+    || aarch64_reg_or_fp_float (operands[1], HFmode))"
   "@
    movi\\t%0.4h, #0
-   mov\\t%0.h[0], %w1
+   fmov\\t%h0, %w1
    umov\\t%w0, %1.h[0]
    mov\\t%0.h[0], %1.h[0]
+   fmov\\t%h0, %1
+   * return aarch64_output_scalar_simd_mov_immediate (operands[1], SImode);
    ldr\\t%h0, %1
    str\\t%h1, %0
    ldrh\\t%w0, %1
    strh\\t%w1, %0
    mov\\t%w0, %w1"
-  [(set_attr "type" "neon_move,neon_from_gp,neon_to_gp,neon_move,\
-                     f_loads,f_stores,load1,store1,mov_reg")
-   (set_attr "simd" "yes,yes,yes,yes,*,*,*,*,*")]
+  [(set_attr "type" "neon_move,f_mcr,neon_to_gp,neon_move,fconsts, \
+		     neon_move,f_loads,f_stores,load1,store1,mov_reg")
+   (set_attr "simd" "yes,*,yes,yes,*,yes,*,*,*,*,*")
+   (set_attr "fp16"   "*,yes,*,*,yes,*,*,*,*,*,*")]
 )
 
 (define_insn "*movsf_aarch64"
-  [(set (match_operand:SF 0 "nonimmediate_operand" "=w,w  ,?r,w,w  ,w,m,r,m ,r")
-	(match_operand:SF 1 "general_operand"      "Y ,?rY, w,w,Ufc,m,w,m,rY,r"))]
+  [(set (match_operand:SF 0 "nonimmediate_operand" "=w,w  ,?r,w,w  ,w  ,w,m,r,m ,r,r")
+	(match_operand:SF 1 "general_operand"      "Y ,?rY, w,w,Ufc,Uvi,m,w,m,rY,r,M"))]
   "TARGET_FLOAT && (register_operand (operands[0], SFmode)
-    || aarch64_reg_or_fp_zero (operands[1], SFmode))"
+    || aarch64_reg_or_fp_float (operands[1], SFmode))"
   "@
    movi\\t%0.2s, #0
    fmov\\t%s0, %w1
    fmov\\t%w0, %s1
    fmov\\t%s0, %s1
    fmov\\t%s0, %1
+   * return aarch64_output_scalar_simd_mov_immediate (operands[1], SImode);
    ldr\\t%s0, %1
    str\\t%s1, %0
    ldr\\t%w0, %1
    str\\t%w1, %0
-   mov\\t%w0, %w1"
-  [(set_attr "type" "neon_move,f_mcr,f_mrc,fmov,fconsts,\
-                     f_loads,f_stores,load1,store1,mov_reg")
-   (set_attr "simd" "yes,*,*,*,*,*,*,*,*,*")]
+   mov\\t%w0, %w1
+   mov\\t%w0, %1"
+  [(set_attr "type" "neon_move,f_mcr,f_mrc,fmov,fconsts,neon_move,\
+		     f_loads,f_stores,load1,store1,mov_reg,\
+		     fconsts")
+   (set_attr "simd" "yes,*,*,*,*,yes,*,*,*,*,*,*")]
 )
 
 (define_insn "*movdf_aarch64"
-  [(set (match_operand:DF 0 "nonimmediate_operand" "=w,w  ,?r,w,w  ,w,m,r,m ,r")
-	(match_operand:DF 1 "general_operand"      "Y ,?rY, w,w,Ufc,m,w,m,rY,r"))]
+  [(set (match_operand:DF 0 "nonimmediate_operand" "=w, w  ,?r,w,w  ,w  ,w,m,r,m ,r,r")
+	(match_operand:DF 1 "general_operand"      "Y , ?rY, w,w,Ufc,Uvi,m,w,m,rY,r,N"))]
   "TARGET_FLOAT && (register_operand (operands[0], DFmode)
-    || aarch64_reg_or_fp_zero (operands[1], DFmode))"
+    || aarch64_reg_or_fp_float (operands[1], DFmode))"
   "@
    movi\\t%d0, #0
    fmov\\t%d0, %x1
    fmov\\t%x0, %d1
    fmov\\t%d0, %d1
    fmov\\t%d0, %1
+   * return aarch64_output_scalar_simd_mov_immediate (operands[1], DImode);
    ldr\\t%d0, %1
    str\\t%d1, %0
    ldr\\t%x0, %1
    str\\t%x1, %0
-   mov\\t%x0, %x1"
-  [(set_attr "type" "neon_move,f_mcr,f_mrc,fmov,fconstd,\
-                     f_loadd,f_stored,load1,store1,mov_reg")
-   (set_attr "simd" "yes,*,*,*,*,*,*,*,*,*")]
+   mov\\t%x0, %x1
+   mov\\t%x0, %1"
+  [(set_attr "type" "neon_move,f_mcr,f_mrc,fmov,fconstd,neon_move,\
+		     f_loadd,f_stored,load1,store1,mov_reg,\
+		     fconstd")
+   (set_attr "simd" "yes,*,*,*,*,yes,*,*,*,*,*,*")]
+)
+
+(define_split
+  [(set (match_operand:GPF_HF 0 "nonimmediate_operand")
+	(match_operand:GPF_HF 1 "general_operand"))]
+  "can_create_pseudo_p ()
+   && !aarch64_can_const_movi_rtx_p (operands[1], <MODE>mode)
+   && !aarch64_float_const_representable_p (operands[1])
+   &&  aarch64_float_const_rtx_p (operands[1])"
+  [(const_int 0)]
+  {
+    unsigned HOST_WIDE_INT ival;
+    if (!aarch64_reinterpret_float_as_int (operands[1], &ival))
+      FAIL;
+
+    rtx tmp = gen_reg_rtx (<FCVT_TARGET>mode);
+    emit_move_insn (tmp, gen_int_mode (ival, <FCVT_TARGET>mode));
+    emit_move_insn (operands[0], gen_lowpart (<MODE>mode, tmp));
+    DONE;
+  }
 )
 
 (define_insn "*movtf_aarch64"
diff --git a/gcc/config/aarch64/iterators.md b/gcc/config/aarch64/iterators.md
index 43be7fd361116d305b0300a814ffca82a9c44a88..067cef785331a243632715e0d0fe35a314eeebff 100644
--- a/gcc/config/aarch64/iterators.md
+++ b/gcc/config/aarch64/iterators.md
@@ -44,6 +44,9 @@
 ;; Iterator for all scalar floating point modes (HF, SF, DF)
 (define_mode_iterator GPF_F16 [(HF "AARCH64_ISA_F16") SF DF])
 
+;; Iterator for all scalar floating point modes (HF, SF, DF)
+(define_mode_iterator GPF_HF [HF SF DF])
+
 ;; Iterator for all scalar floating point modes (HF, SF, DF and TF)
 (define_mode_iterator GPF_TF_F16 [HF SF DF TF])