[PATCH] bitint: Handle VCE from large/huge _BitInt SSA_NAME from load [PR114156]

[Jakub Jelinek]

Hi!

When adding checks in which case not to merge a VIEW_CONVERT_EXPR from
large/huge _BitInt to vector/complex etc., I missed the case of loads.
Those are handled differently later.
Anyway, I think the load case is something we can handle just fine,
so the following patch does that instead of preventing the merging
gimple_lower_bitint; we'd then copy from memory to memory and and do the
vce only on the second one, it is just better to vce the first one.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2024-03-01  Jakub Jelinek  <ja...@redhat.com>

        PR middle-end/114156
        * gimple-lower-bitint.cc (bitint_large_huge::lower_stmt): Allow
        rhs1 of a VCE to have no underlying variable if it is a load and
        handle that case.

        * gcc.dg/bitint-96.c: New test.

--- gcc/gimple-lower-bitint.cc.jj       2024-02-24 12:44:27.993108306 +0100
+++ gcc/gimple-lower-bitint.cc  2024-02-29 19:28:59.442020619 +0100
@@ -5329,6 +5329,22 @@ bitint_large_huge::lower_stmt (gimple *s
                  gimple_assign_set_rhs1 (stmt, rhs1);
                  gimple_assign_set_rhs_code (stmt, SSA_NAME);
                }
+             else if (m_names == NULL
+                      || !bitmap_bit_p (m_names, SSA_NAME_VERSION (rhs1)))
+               {
+                 gimple *g = SSA_NAME_DEF_STMT (rhs1);
+                 gcc_assert (gimple_assign_load_p (g));
+                 tree mem = gimple_assign_rhs1 (g);
+                 tree ltype = TREE_TYPE (lhs);
+                 addr_space_t as = TYPE_ADDR_SPACE (TREE_TYPE (mem));
+                 if (as != TYPE_ADDR_SPACE (ltype))
+                   ltype
+                     = build_qualified_type (ltype,
+                                             TYPE_QUALS (ltype)
+                                             | ENCODE_QUAL_ADDR_SPACE (as));
+                 rhs1 = build1 (VIEW_CONVERT_EXPR, ltype, mem);
+                 gimple_assign_set_rhs1 (stmt, rhs1);
+               }
              else
                {
                  int part = var_to_partition (m_map, rhs1);
--- gcc/testsuite/gcc.dg/bitint-96.c.jj 2024-02-29 19:37:27.441032088 +0100
+++ gcc/testsuite/gcc.dg/bitint-96.c    2024-02-29 19:36:34.815753879 +0100
@@ -0,0 +1,17 @@
+/* PR middle-end/114156 */
+/* { dg-do compile { target bitint } } */
+/* { dg-options "-O2" } */
+/* { dg-additional-options "-msse2" { target i?86-*-* x86_64-*-* } } */
+
+#if __BITINT_MAXWIDTH__ >= 128
+_BitInt(128) a, b;
+#else
+int a, b;
+#endif
+
+void
+foo (void)
+{
+  int u = b;
+  __builtin_memmove (&a, &b, sizeof (a));
+}

        Jakub