Hi,
This is a rebased version of patch that adds a pattern to neon.md for
implementing division with multiplication by reciprocal using
vrecpe/vrecps with -funsafe-math-optimizations excluding -Os.
The newly added test-cases are not vectorized on armeb target with
-O2. I posted the analysis for that here:
https://gcc.gnu.org/ml/gcc-patches/2016-05/msg01765.html
Briefly, the difference between little and big-endian vectorizer is in
arm_builtin_support_vector_misalignment() which calls
default_builtin_support_vector_misalignment() for big-endian case, and
that returns false because
movmisalign_optab does not exist for V2SF mode. This isn't observed
with -O3 because loop peeling for alignment gets enabled.
It seems that the test cases in patch appear unsupported on armeb,
after r221677 thus this patch requires no changes to
target-supports.exp to adjust for armeb (unlike last time which
stalled the patch).
Bootstrap+tested on arm-linux-gnueabihf.
Cross-tested on arm*-*-* variants.
OK for trunk ?
Thanks,
Prathamesh
2018-10-26 Prathamesh Kulkarni <prathamesh.kulka...@linaro.org>
* config/arm/neon.md (div<mode>3): New pattern.
testsuite/
* gcc.target/arm/neon-vect-div-1.c: New test.
* gcc.target/arm/neon-vect-div-2.c: Likewise.
diff --git a/gcc/config/arm/neon.md b/gcc/config/arm/neon.md
index 5aeee4b08c1..25ed45d381a 100644
--- a/gcc/config/arm/neon.md
+++ b/gcc/config/arm/neon.md
@@ -620,6 +620,38 @@
(const_string "neon_mul_<V_elem_ch><q>")))]
)
+/* Perform division using multiply-by-reciprocal.
+ Reciprocal is calculated using Newton-Raphson method.
+ Enabled with -funsafe-math-optimizations -freciprocal-math
+ and disabled for -Os since it increases code size . */
+
+(define_expand "div<mode>3"
+ [(set (match_operand:VCVTF 0 "s_register_operand" "=w")
+ (div:VCVTF (match_operand:VCVTF 1 "s_register_operand" "w")
+ (match_operand:VCVTF 2 "s_register_operand" "w")))]
+ "TARGET_NEON && !optimize_size
+ && flag_unsafe_math_optimizations && flag_reciprocal_math"
+ {
+ rtx rec = gen_reg_rtx (<MODE>mode);
+ rtx vrecps_temp = gen_reg_rtx (<MODE>mode);
+
+ /* Reciprocal estimate. */
+ emit_insn (gen_neon_vrecpe<mode> (rec, operands[2]));
+
+ /* Perform 2 iterations of newton-raphson method. */
+ for (int i = 0; i < 2; i++)
+ {
+ emit_insn (gen_neon_vrecps<mode> (vrecps_temp, rec, operands[2]));
+ emit_insn (gen_mul<mode>3 (rec, rec, vrecps_temp));
+ }
+
+ /* We now have reciprocal in rec, perform operands[0] = operands[1] * rec.
*/
+ emit_insn (gen_mul<mode>3 (operands[0], operands[1], rec));
+ DONE;
+ }
+)
+
+
(define_insn "mul<mode>3add<mode>_neon"
[(set (match_operand:VDQW 0 "s_register_operand" "=w")
(plus:VDQW (mult:VDQW (match_operand:VDQW 2 "s_register_operand" "w")
diff --git a/gcc/testsuite/gcc.target/arm/neon-vect-div-1.c
b/gcc/testsuite/gcc.target/arm/neon-vect-div-1.c
new file mode 100644
index 00000000000..50d04b4175b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/neon-vect-div-1.c
@@ -0,0 +1,16 @@
+/* Test pattern div<mode>3. */
+/* { dg-do compile } */
+/* { dg-require-effective-target arm_neon_ok } */
+/* { dg-require-effective-target vect_hw_misalign } */
+/* { dg-options "-O2 -ftree-vectorize -funsafe-math-optimizations
-fdump-tree-vect-details" } */
+/* { dg-add-options arm_neon } */
+
+void
+foo (int len, float * __restrict p, float *__restrict x)
+{
+ len = len & ~31;
+ for (int i = 0; i < len; i++)
+ p[i] = p[i] / x[i];
+}
+
+/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" } } */
diff --git a/gcc/testsuite/gcc.target/arm/neon-vect-div-2.c
b/gcc/testsuite/gcc.target/arm/neon-vect-div-2.c
new file mode 100644
index 00000000000..606f54b4e0e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/neon-vect-div-2.c
@@ -0,0 +1,16 @@
+/* Test pattern div<mode>3. */
+/* { dg-do compile } */
+/* { dg-require-effective-target arm_neon_ok } */
+/* { dg-require-effective-target vect_hw_misalign } */
+/* { dg-options "-O3 -ftree-vectorize -funsafe-math-optimizations
-fdump-tree-vect-details -fno-reciprocal-math" } */
+/* { dg-add-options arm_neon } */
+
+void
+foo (int len, float * __restrict p, float *__restrict x)
+{
+ len = len & ~31;
+ for (int i = 0; i < len; i++)
+ p[i] = p[i] / x[i];
+}
+
+/* { dg-final { scan-tree-dump-not "vectorized 1 loops" "vect" } } */
