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[AArch64][SVE] Remove unnecessary PTRUEs from FP arithmetic


When using the unpredicated all-register forms of FADD, FSUB and FMUL,
the rtl patterns would still have the predicate operand we created for
the other forms.  This patch splits the patterns after reload in order
to get rid of the predicate, like we already do for WHILE.

Tested on aarch64-linux-gnu and applied.

Richard


2018-12-07  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/iterators.md (SVE_UNPRED_FP_BINARY): New code
	iterator.
	(sve_fp_op): Handle minus and mult.
	* config/aarch64/aarch64-sve.md (*add<mode>3, *sub<mode>3)
	(*mul<mode>3): Split the patterns after reload if we don't
	need the predicate operand.
	(*post_ra_<sve_fp_op><mode>3): New pattern.

gcc/testsuite/
	* gcc.target/aarch64/sve/pred_elim_1.c: New test.

Index: gcc/config/aarch64/iterators.md
===================================================================
--- gcc/config/aarch64/iterators.md	2018-12-05 08:33:40.970920085 +0000
+++ gcc/config/aarch64/iterators.md	2018-12-07 14:59:39.875208953 +0000
@@ -1220,6 +1220,9 @@ (define_code_iterator SVE_INT_BINARY [pl
 ;; SVE integer binary division operations.
 (define_code_iterator SVE_INT_BINARY_SD [div udiv])
 
+;; SVE floating-point operations with an unpredicated all-register form.
+(define_code_iterator SVE_UNPRED_FP_BINARY [plus minus mult])
+
 ;; SVE integer comparisons.
 (define_code_iterator SVE_INT_CMP [lt le eq ne ge gt ltu leu geu gtu])
 
@@ -1423,6 +1426,8 @@ (define_code_attr sve_int_op_rev [(plus
 
 ;; The floating-point SVE instruction that implements an rtx code.
 (define_code_attr sve_fp_op [(plus "fadd")
+			     (minus "fsub")
+			     (mult "fmul")
 			     (neg "fneg")
 			     (abs "fabs")
 			     (sqrt "fsqrt")])
Index: gcc/config/aarch64/aarch64-sve.md
===================================================================
--- gcc/config/aarch64/aarch64-sve.md	2018-07-18 18:44:56.000000000 +0100
+++ gcc/config/aarch64/aarch64-sve.md	2018-12-07 14:59:39.875208953 +0000
@@ -2194,7 +2194,7 @@ (define_expand "add<mode>3"
 )
 
 ;; Floating-point addition predicated with a PTRUE.
-(define_insn "*add<mode>3"
+(define_insn_and_split "*add<mode>3"
   [(set (match_operand:SVE_F 0 "register_operand" "=w, w, w")
 	(unspec:SVE_F
 	  [(match_operand:<VPRED> 1 "register_operand" "Upl, Upl, Upl")
@@ -2206,7 +2206,12 @@ (define_insn "*add<mode>3"
   "@
    fadd\t%0.<Vetype>, %1/m, %0.<Vetype>, #%3
    fsub\t%0.<Vetype>, %1/m, %0.<Vetype>, #%N3
-   fadd\t%0.<Vetype>, %2.<Vetype>, %3.<Vetype>"
+   #"
+  ; Split the unpredicated form after reload, so that we don't have
+  ; the unnecessary PTRUE.
+  "&& reload_completed
+   && register_operand (operands[3], <MODE>mode)"
+  [(set (match_dup 0) (plus:SVE_F (match_dup 2) (match_dup 3)))]
 )
 
 ;; Unpredicated floating-point subtraction.
@@ -2225,7 +2230,7 @@ (define_expand "sub<mode>3"
 )
 
 ;; Floating-point subtraction predicated with a PTRUE.
-(define_insn "*sub<mode>3"
+(define_insn_and_split "*sub<mode>3"
   [(set (match_operand:SVE_F 0 "register_operand" "=w, w, w, w")
 	(unspec:SVE_F
 	  [(match_operand:<VPRED> 1 "register_operand" "Upl, Upl, Upl, Upl")
@@ -2240,7 +2245,13 @@ (define_insn "*sub<mode>3"
    fsub\t%0.<Vetype>, %1/m, %0.<Vetype>, #%3
    fadd\t%0.<Vetype>, %1/m, %0.<Vetype>, #%N3
    fsubr\t%0.<Vetype>, %1/m, %0.<Vetype>, #%2
-   fsub\t%0.<Vetype>, %2.<Vetype>, %3.<Vetype>"
+   #"
+  ; Split the unpredicated form after reload, so that we don't have
+  ; the unnecessary PTRUE.
+  "&& reload_completed
+   && register_operand (operands[2], <MODE>mode)
+   && register_operand (operands[3], <MODE>mode)"
+  [(set (match_dup 0) (minus:SVE_F (match_dup 2) (match_dup 3)))]
 )
 
 ;; Unpredicated floating-point multiplication.
@@ -2259,7 +2270,7 @@ (define_expand "mul<mode>3"
 )
 
 ;; Floating-point multiplication predicated with a PTRUE.
-(define_insn "*mul<mode>3"
+(define_insn_and_split "*mul<mode>3"
   [(set (match_operand:SVE_F 0 "register_operand" "=w, w")
 	(unspec:SVE_F
 	  [(match_operand:<VPRED> 1 "register_operand" "Upl, Upl")
@@ -2270,8 +2281,24 @@ (define_insn "*mul<mode>3"
   "TARGET_SVE"
   "@
    fmul\t%0.<Vetype>, %1/m, %0.<Vetype>, #%3
-   fmul\t%0.<Vetype>, %2.<Vetype>, %3.<Vetype>"
-)
+   #"
+  ; Split the unpredicated form after reload, so that we don't have
+  ; the unnecessary PTRUE.
+  "&& reload_completed
+   && register_operand (operands[3], <MODE>mode)"
+  [(set (match_dup 0) (mult:SVE_F (match_dup 2) (match_dup 3)))]
+)
+
+;; Unpredicated floating-point binary operations (post-RA only).
+;; These are generated by splitting a predicated instruction whose
+;; predicate is unused.
+(define_insn "*post_ra_<sve_fp_op><mode>3"
+  [(set (match_operand:SVE_F 0 "register_operand" "=w")
+	(SVE_UNPRED_FP_BINARY:SVE_F
+	  (match_operand:SVE_F 1 "register_operand" "w")
+	  (match_operand:SVE_F 2 "register_operand" "w")))]
+  "TARGET_SVE && reload_completed"
+  "<sve_fp_op>\t%0.<Vetype>, %1.<Vetype>, %2.<Vetype>")
 
 ;; Unpredicated fma (%0 = (%1 * %2) + %3).
 (define_expand "fma<mode>4"
Index: gcc/testsuite/gcc.target/aarch64/sve/pred_elim_1.c
===================================================================
--- /dev/null	2018-11-29 13:15:04.463550658 +0000
+++ gcc/testsuite/gcc.target/aarch64/sve/pred_elim_1.c	2018-12-07 14:59:39.875208953 +0000
@@ -0,0 +1,23 @@
+/* { dg-options "-O2 -ftree-vectorize" } */
+
+#define TEST_OP(NAME, TYPE, OP)				\
+  void							\
+  NAME##_##TYPE (TYPE *restrict a, TYPE *restrict b,	\
+		 TYPE *restrict c, int n)		\
+  {							\
+    for (int i = 0; i < n; ++i)				\
+      a[i] = b[i] OP c[i];				\
+  }
+
+#define TEST_TYPE(TYPE) \
+  TEST_OP (add, TYPE, +) \
+  TEST_OP (sub, TYPE, -) \
+  TEST_OP (mult, TYPE, *) \
+
+TEST_TYPE (float)
+TEST_TYPE (double)
+
+/* { dg-final { scan-assembler-times {\tfadd\t} 2 } } */
+/* { dg-final { scan-assembler-times {\tfsub\t} 2 } } */
+/* { dg-final { scan-assembler-times {\tfmul\t} 2 } } */
+/* { dg-final { scan-assembler-not {\tptrue\t} } } */


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