[gcc r14-3099] RISC-V: Support NPATTERNS = 1 stepped vector[PR110950]

[gcc r14-3099] RISC-V: Support NPATTERNS = 1 stepped vector[PR110950]

[Pan Li]

https://gcc.gnu.org/g:c4d618143048ac781f435638ef6e788ba870dc53

commit r14-3099-gc4d618143048ac781f435638ef6e788ba870dc53
Author: Juzhe-Zhong <juzhe.zhong@rivai.ai>
Date:   Wed Aug 9 20:18:40 2023 +0800

    RISC-V: Support NPATTERNS = 1 stepped vector[PR110950]
    
    This patch fix ICE: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110950
    
    0x1cf8939 expand_const_vector
            ../../../riscv-gcc/gcc/config/riscv/riscv-v.cc:1587
    
            PR target/110950
    
    gcc/ChangeLog:
    
            * config/riscv/riscv-v.cc (expand_const_vector): Add NPATTERNS = 1
            stepped vector support.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/riscv/rvv/autovec/pr110950.c: New test.

Diff:
---
 gcc/config/riscv/riscv-v.cc                           | 19 +++++++++++++++++++
 gcc/testsuite/gcc.target/riscv/rvv/autovec/pr110950.c | 12 ++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/gcc/config/riscv/riscv-v.cc b/gcc/config/riscv/riscv-v.cc
index a7b2d7dd2fe0..0bea04c1967e 100644
--- a/gcc/config/riscv/riscv-v.cc
+++ b/gcc/config/riscv/riscv-v.cc
@@ -1563,6 +1563,25 @@ expand_const_vector (rtx target, rtx src)
 			       add_ops);
 	    }
 	}
+      else if (npatterns == 1 && nelts_per_pattern == 3)
+	{
+	  /* Generate the following CONST_VECTOR:
+	     { base0, base1, base1 + step, base1 + step * 2, ... }  */
+	  rtx base0 = CONST_VECTOR_ELT (src, 0);
+	  rtx base1 = CONST_VECTOR_ELT (src, 1);
+	  rtx step = CONST_VECTOR_ELT (src, 2);
+	  /* Step 1 - { base1, base1 + step, base1 + step * 2, ... }  */
+	  rtx tmp = gen_reg_rtx (mode);
+	  emit_insn (gen_vec_series (mode, tmp, base1, step));
+	  /* Step 2 - { base0, base1, base1 + step, base1 + step * 2, ... }  */
+	  scalar_mode elem_mode = GET_MODE_INNER (mode);
+	  if (!rtx_equal_p (base0, const0_rtx))
+	    base0 = force_reg (elem_mode, base0);
+
+	  insn_code icode = optab_handler (vec_shl_insert_optab, mode);
+	  gcc_assert (icode != CODE_FOR_nothing);
+	  emit_insn (GEN_FCN (icode) (target, tmp, base0));
+	}
       else
 	/* TODO: We will enable more variable-length vector in the future.  */
 	gcc_unreachable ();
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr110950.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr110950.c
new file mode 100644
index 000000000000..9f276d06338b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr110950.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d --param=riscv-autovec-preference=scalable -Ofast" } */
+
+int a;
+void b() {
+  long *c = 0;
+  int *d;
+  for (; a; ++a)
+    c[a] = d[-a];
+}
+
+/* { dg-final { scan-assembler-times {vslide1up\.vx} 1 } } */