[ARM] PR97906 - Missed lowering abs(a) >= abs(b) to vacge

Prathamesh Kulkarni prathamesh.kulkarni@linaro.org
Tue Jun 1 10:33:01 GMT 2021


Hi,
As mentioned in PR, for following test-case:

#include <arm_neon.h>

uint32x2_t f1(float32x2_t a, float32x2_t b)
{
  return vabs_f32 (a) >= vabs_f32 (b);
}

uint32x2_t f2(float32x2_t a, float32x2_t b)
{
  return (uint32x2_t) __builtin_neon_vcagev2sf (a, b);
}

We generate vacge for f2, but with -ffast-math, we generate following for f1:
f1:
        vabs.f32        d1, d1
        vabs.f32        d0, d0
        vcge.f32        d0, d0, d1
        bx      lr

This happens because, the middle-end inverts the comparison to b <= a,
.optimized dump:
 _8 = __builtin_neon_vabsv2sf (a_4(D));
  _7 = __builtin_neon_vabsv2sf (b_5(D));
  _1 = _7 <= _8;
  _2 = VIEW_CONVERT_EXPR<vector(2) int>(_1);
  _6 = VIEW_CONVERT_EXPR<uint32x2_t>(_2);
  return _6;

and combine fails to match the following pattern:
(set (reg:V2SI 121)
    (neg:V2SI (le:V2SI (abs:V2SF (reg:V2SF 123))
            (abs:V2SF (reg:V2SF 122)))))

because neon_vca<cmp_op><mode> pattern has GTGE code iterator.
The attached patch adjusts the neon_vca patterns to use GLTE instead
similar to neon_vca<cmp_op><mode>_fp16insn, and removes NEON_VACMP iterator.
Code-gen with patch:
f1:
        vacle.f32       d0, d1, d0
        bx      lr

Bootstrapped + tested on arm-linux-gnueabihf and cross-tested on arm*-*-*.
OK to commit ?

Thanks,
Prathamesh
-------------- next part --------------
2021-06-01  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>

        PR target/97906
        * config/arm/iterators.md (NEON_VACMP): Remove.
        * config/arm/neon.md (neon_vca<cmp_op><mode>): Use GLTE instead of GTGE iterator.
        (neon_vca<cmp_op><mode>_insn): Likewise.
        (neon_vca<cmp_op_unsp><mode>_insn_unspec): Use NEON_VAGLTE instead of NEON_VACMP.

testsuite/
	* gcc.target/arm/simd/pr97906.c: New test.

diff --git a/gcc/config/arm/iterators.md b/gcc/config/arm/iterators.md
index 3042bafc6c6..0e0e825225a 100644
--- a/gcc/config/arm/iterators.md
+++ b/gcc/config/arm/iterators.md
@@ -364,8 +364,6 @@
 (define_int_iterator NEON_VCMP [UNSPEC_VCEQ UNSPEC_VCGT UNSPEC_VCGE
 				UNSPEC_VCLT UNSPEC_VCLE])
 
-(define_int_iterator NEON_VACMP [UNSPEC_VCAGE UNSPEC_VCAGT])
-
 (define_int_iterator NEON_VAGLTE [UNSPEC_VCAGE UNSPEC_VCAGT
 				  UNSPEC_VCALE UNSPEC_VCALT])
 
diff --git a/gcc/config/arm/neon.md b/gcc/config/arm/neon.md
index cc82d068a1c..ccc99603531 100644
--- a/gcc/config/arm/neon.md
+++ b/gcc/config/arm/neon.md
@@ -2400,7 +2400,7 @@
 (define_expand "neon_vca<cmp_op><mode>"
   [(set (match_operand:<V_cmp_result> 0 "s_register_operand")
         (neg:<V_cmp_result>
-          (GTGE:<V_cmp_result>
+          (GLTE:<V_cmp_result>
             (abs:VCVTF (match_operand:VCVTF 1 "s_register_operand"))
             (abs:VCVTF (match_operand:VCVTF 2 "s_register_operand")))))]
   "TARGET_NEON"
@@ -2419,7 +2419,7 @@
 (define_insn "neon_vca<cmp_op><mode>_insn"
   [(set (match_operand:<V_cmp_result> 0 "s_register_operand" "=w")
         (neg:<V_cmp_result>
-          (GTGE:<V_cmp_result>
+          (GLTE:<V_cmp_result>
             (abs:VCVTF (match_operand:VCVTF 1 "s_register_operand" "w"))
             (abs:VCVTF (match_operand:VCVTF 2 "s_register_operand" "w")))))]
   "TARGET_NEON && flag_unsafe_math_optimizations"
@@ -2431,7 +2431,7 @@
   [(set (match_operand:<V_cmp_result> 0 "s_register_operand" "=w")
         (unspec:<V_cmp_result> [(match_operand:VCVTF 1 "s_register_operand" "w")
 		                (match_operand:VCVTF 2 "s_register_operand" "w")]
-                               NEON_VACMP))]
+                               NEON_VAGLTE))]
   "TARGET_NEON"
   "vac<cmp_op_unsp>.<V_if_elem>\t%<V_reg>0, %<V_reg>1, %<V_reg>2"
   [(set_attr "type" "neon_fp_compare_s<q>")]
diff --git a/gcc/testsuite/gcc.target/arm/simd/pr97906.c b/gcc/testsuite/gcc.target/arm/simd/pr97906.c
new file mode 100644
index 00000000000..7c972e311ed
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/simd/pr97906.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -ffast-math" } */
+/* { dg-add-options arm_neon } */
+
+#include <arm_neon.h>
+
+uint32x2_t f1(float32x2_t a, float32x2_t b)
+{
+  return vabs_f32 (a) >= vabs_f32 (b);
+}
+
+/* { dg-final { scan-assembler-times {\tvacle.f32\td[0-9]+, d[0-9]+, d[0-9]+} 1 } } */
+/* { dg-final { scan-assembler-not "vabs" } } */


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