[PATCH] RISC-V: Correct mode_idx attribute for viwalu wx variants [PR116149].

[Robin Dapp]

Hi,

in PR116149 we choose a wrong vector length which causes wrong values in
a reduction.  The problem happens in avlprop where we choose the
number of units in the instruction's mode as vector length.  For the
non-scalar variants the respective operand has the correct non-widened
mode.  For the scalar variants, however, the same operand has a scalar
mode which obviously only has one unit.  This makes us choose VL = 1
leaving three elements undisturbed (so potentially -1).  Those end up
in the reduction causing the wrong result.

This patch adjusts the mode_idx just for the scalar variants of the
affected instruction patterns.

Regards
 Robin

gcc/ChangeLog:

	PR target/116149

	* config/riscv/vector.md: Fix mode_idx attribute of scalar
	widen add/sub variants.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/pr116149.c: New test.
---
 gcc/config/riscv/vector.md                     |  2 ++
 .../gcc.target/riscv/rvv/autovec/pr116149.c    | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/pr116149.c

diff --git a/gcc/config/riscv/vector.md b/gcc/config/riscv/vector.md
index bcedf3d79e2..d4d9bd87e91 100644
--- a/gcc/config/riscv/vector.md
+++ b/gcc/config/riscv/vector.md
@@ -4016,6 +4016,7 @@ (define_insn "@pred_single_widen_add<any_extend:su><mode>_extended_scalar"
   "TARGET_VECTOR"
   "vwadd<any_extend:u>.wx\t%0,%3,%z4%p1"
   [(set_attr "type" "viwalu")
+   (set_attr "mode_idx" "3")
    (set_attr "mode" "<V_DOUBLE_TRUNC>")])
 
 (define_insn "@pred_single_widen_sub<any_extend:su><mode>_extended_scalar"
@@ -4038,6 +4039,7 @@ (define_insn "@pred_single_widen_sub<any_extend:su><mode>_extended_scalar"
   "TARGET_VECTOR"
   "vwsub<any_extend:u>.wx\t%0,%3,%z4%p1"
   [(set_attr "type" "viwalu")
+   (set_attr "mode_idx" "3")
    (set_attr "mode" "<V_DOUBLE_TRUNC>")])
 
 (define_insn "@pred_widen_mulsu<mode>"
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr116149.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr116149.c
new file mode 100644
index 00000000000..4f5927b96fe
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr116149.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -march=rv64gcv_zvl256b -mabi=lp64d -mrvv-vector-bits=zvl" } */
+
+long a;
+short b[60000];
+short c[20];
+int main() {
+  for (short d = 0; d < 20; d += 3) {
+    c[d] = 0;
+    for (int e = 0; e < 20; e += 2)
+      for (int f = 1; f < 20; f += 2)
+        a += (unsigned)b[f + e];
+  }
+  if (a != 0)
+    __builtin_abort ();
+}
+
+/* { dg-final { scan-assembler-times "vsetivli\tzero,1" 0 } } */
-- 
2.45.2