[gcc r15-8084] RISC-V: Mask values before initializing bitmask vector [PR119114].

[Robin Dapp via Gcc-cvs]

https://gcc.gnu.org/g:b58a0af4e2e28b395a3cb4b7283f16f05c0cf3c8

commit r15-8084-gb58a0af4e2e28b395a3cb4b7283f16f05c0cf3c8
Author: Robin Dapp <rd...@ventanamicro.com>
Date:   Tue Mar 11 14:30:48 2025 +0100

    RISC-V: Mask values before initializing bitmask vector [PR119114].
    
    In the somewhat convoluted vector code of PR119114 we extract a
    <signed-boolean:1> mask value from a vector mask.  After some middle-end
    simplifications we end up with a value of -2.  Its lowest bit is
    correctly unset representing "false".  When initializing a bitmak vector
    from values we compare the full value/register against zero instead of
    just the last bit.  This causes erroneous mask values.
    
    This patch masks the values by & 0x1 before comparing against 0.
    
            PR target/119114
    
    gcc/ChangeLog:
    
            * config/riscv/autovec.md: Apply & 0x1 mask when initializing
            bitmask vector.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/riscv/rvv/autovec/pr119114.c: New test.

Diff:
---
 gcc/config/riscv/autovec.md                        | 14 +++++++-
 .../gcc.target/riscv/rvv/autovec/pr119114.c        | 37 ++++++++++++++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/gcc/config/riscv/autovec.md b/gcc/config/riscv/autovec.md
index 92e6942b5233..c7f12f9e36f5 100644
--- a/gcc/config/riscv/autovec.md
+++ b/gcc/config/riscv/autovec.md
@@ -405,16 +405,28 @@
 
 ;; Provide a vec_init for mask registers by initializing
 ;; a QImode vector and comparing it against 0.
+;; As we need to ignore all but the lowest bit apply an AND mask
+;; before doing the comparison.
 (define_expand "vec_init<mode>qi"
   [(match_operand:VB 0 "register_operand")
    (match_operand 1 "")]
   "TARGET_VECTOR"
   {
+    /* Expand into a QImode vector.  */
     machine_mode qimode = riscv_vector::get_vector_mode
        (QImode, GET_MODE_NUNITS (<MODE>mode)).require ();
     rtx tmp = gen_reg_rtx (qimode);
     riscv_vector::expand_vec_init (tmp, operands[1]);
-    riscv_vector::expand_vec_cmp (operands[0], NE, tmp, CONST0_RTX (qimode));
+
+    /* & 0x1.  */
+    insn_code icode = code_for_pred (AND, qimode);
+    rtx tmp2 = gen_reg_rtx (qimode);
+    rtx ones = gen_const_vec_duplicate (qimode, GEN_INT (1));
+    rtx ops[] = {tmp2, tmp, ones};
+    riscv_vector::emit_vlmax_insn (icode, riscv_vector::BINARY_OP, ops);
+
+    /* Compare against zero.  */
+    riscv_vector::expand_vec_cmp (operands[0], NE, tmp2, CONST0_RTX (qimode));
     DONE;
   }
 )
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr119114.c 
b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr119114.c
new file mode 100644
index 000000000000..01025d62f1fd
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr119114.c
@@ -0,0 +1,37 @@
+/* { dg-do run } */
+/* { dg-require-effective-target riscv_v_ok } */
+/* { dg-require-effective-target rv64 } */
+/* { dg-add-options riscv_v } */
+/* { dg-options "-O3 -march=rv64gcv -mabi=lp64d -std=gnu99 -fwhole-program 
-mrvv-vector-bits=zvl" } */
+
+_Bool a;
+short b[18];
+long long al;
+_Bool e;
+char f = 010;
+short t[18];
+unsigned short w[8][18][18][18];
+
+void
+c (_Bool e, char f, short t[], unsigned short w[][18][18][18])
+{
+  for (int ae = 1; ae < f + 5; ae += 2)
+    {
+      a -= (_Bool) (t[ae - 1] & t[ae + 3]);
+      for (short af = 0; af < 18; af += 2)
+       for (_Bool ah = 0; ah < (w[e][1][af][0] > 0); ah = 5)
+         b[af] |= 9;
+    }
+}
+
+int
+main ()
+{
+  for (int ad = 0; ad < 18; ad++)
+    t[ad] = 3;
+
+  c (e, f, t, w);
+  al = a;
+  if (al != 0)
+    __builtin_abort ();
+}