From: Jeff Law <jlaw@ventanamicro.com>
Date: Wed, 9 Jul 2025 11:23:34 +0000 (-0600)
Subject: [RISC-V][PR target/120642] Avoid propagating constant AVL for theadvector
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f2e3886a30c771b104bc2714992e072b21a52e76;p=thirdparty%2Fgcc.git

[RISC-V][PR target/120642] Avoid propagating constant AVL for theadvector

AVL propagation currently assumes that it can propagate a constant AVL into any
vector insn and trips an assert if the insn fails to recognize after such a
propagation.

However, for xtheadvector that is not a correct assumption; xtheadvector does
not allow the vector length to be a constant integer (other than zero which
allowed via x0).

After consulting with Jin Ma (thanks!) we agree the right fix is to avoid
creating the immediate AVL for xtheadvector.

This has been tested in my tester, just waiting for the pre-commit tester to
spin it.

	PR target/120642
gcc/
	* config/riscv/riscv-avlprop.cc (pass_avlprop::execute): Do not do
	constant AVL propagation for xtheadvector.

gcc/testsuite/
	* gcc.target/riscv/rvv/xtheadvector/pr120642.c: New test.
---

diff --git a/gcc/config/riscv/riscv-avlprop.cc b/gcc/config/riscv/riscv-avlprop.cc
index bb4aceb7506..3031c29ae63 100644
--- a/gcc/config/riscv/riscv-avlprop.cc
+++ b/gcc/config/riscv/riscv-avlprop.cc
@@ -508,7 +508,7 @@ pass_avlprop::execute (function *fn)
       simplify_replace_vlmax_avl (rinsn, prop.second);
     }
 
-  if (rvv_vector_bits == RVV_VECTOR_BITS_ZVL)
+  if (rvv_vector_bits == RVV_VECTOR_BITS_ZVL && !TARGET_XTHEADVECTOR)
     {
       /* Simplify VLMAX AVL into immediate AVL.
 	 E.g. Simplify this following case:
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/xtheadvector/pr120642.c b/gcc/testsuite/gcc.target/riscv/rvv/xtheadvector/pr120642.c
new file mode 100644
index 00000000000..1a72580ad60
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/xtheadvector/pr120642.c
@@ -0,0 +1,4 @@
+/* { dg-do compile } */
+/* { dg-options "-O -mcpu=xt-c920 -mrvv-vector-bits=zvl" } */
+int __attribute__((__vector_size__(4 * sizeof(int)))) v;
+void foo() { v /= 3; }