RISC-V: Disable user vsetvl fusion into EMPTY or DIRTY (Polluted EMPTY) block

This patch is fixing these bunch of ICE in "vect" testsuite:
FAIL: gcc.dg/vect/no-scevccp-outer-2.c (internal compiler error: in anticipatable_occurrence_p, at config/riscv/riscv-vsetvl.cc:314)
FAIL: gcc.dg/vect/no-scevccp-outer-2.c (test for excess errors)
FAIL: gcc.dg/vect/pr109025.c (internal compiler error: in anticipatable_occurrence_p, at config/riscv/riscv-vsetvl.cc:314)
FAIL: gcc.dg/vect/pr109025.c (test for excess errors)
FAIL: gcc.dg/vect/pr109025.c -flto -ffat-lto-objects (internal compiler error: in anticipatable_occurrence_p, at config/riscv/riscv-vsetvl.cc:314)
FAIL: gcc.dg/vect/pr109025.c -flto -ffat-lto-objects (test for excess errors)
FAIL: gcc.dg/vect/pr42604.c (internal compiler error: in anticipatable_occurrence_p, at config/riscv/riscv-vsetvl.cc:314)
FAIL: gcc.dg/vect/pr42604.c (test for excess errors)
FAIL: gcc.dg/vect/pr42604.c -flto -ffat-lto-objects (internal compiler error: in anticipatable_occurrence_p, at config/riscv/riscv-vsetvl.cc:314)
FAIL: gcc.dg/vect/pr42604.c -flto -ffat-lto-objects (test for excess errors)
FAIL: gcc.dg/vect/vect-double-reduc-3.c (internal compiler error: in anticipatable_occurrence_p, at config/riscv/riscv-vsetvl.cc:314)
FAIL: gcc.dg/vect/vect-double-reduc-3.c (test for excess errors)
FAIL: gcc.dg/vect/vect-double-reduc-3.c -flto -ffat-lto-objects (internal compiler error: in anticipatable_occurrence_p, at config/riscv/riscv-vsetvl.cc:314)
FAIL: gcc.dg/vect/vect-double-reduc-3.c -flto -ffat-lto-objects (test for excess errors)
FAIL: gcc.dg/vect/vect-double-reduc-7.c (internal compiler error: in anticipatable_occurrence_p, at config/riscv/riscv-vsetvl.cc:314)
FAIL: gcc.dg/vect/vect-double-reduc-7.c (test for excess errors)
FAIL: gcc.dg/vect/vect-double-reduc-7.c -flto -ffat-lto-objects (internal compiler error: in anticipatable_occurrence_p, at config/riscv/riscv-vsetvl.cc:314)
FAIL: gcc.dg/vect/vect-double-reduc-7.c -flto -ffat-lto-objects (test for excess errors)

gcc/ChangeLog:

	* config/riscv/riscv-vsetvl.cc (pass_vsetvl::earliest_fusion): Fix bug.

diff --git a/gcc/config/riscv/riscv-vsetvl.cc b/gcc/config/riscv/riscv-vsetvl.cc
index 682f795c8e1166ad779cdb2b575e3ba89e21b458..48e89fe2c0373d4cd698aa783e98516137ac9b5e 100644 (file)
--- a/gcc/config/riscv/riscv-vsetvl.cc
+++ b/gcc/config/riscv/riscv-vsetvl.cc
@@ -3285,12 +3285,46 @@ pass_vsetvl::earliest_fusion (void)
              gcc_assert (!(eg->flags & EDGE_ABNORMAL));
              vector_insn_info new_info = vector_insn_info ();
              profile_probability prob = src_block_info.probability;
+             /* We don't fuse user vsetvl into EMPTY or
+                DIRTY (EMPTY but polluted) block for these
+                following reasons:
+
+               - The user vsetvl instruction is configured as
+                 no side effects that the previous passes
+                 (GSCE, Loop-invariant, ..., etc)
+                 should be able to do a good job on optimization
+                 of user explicit vsetvls so we don't need to
+                 PRE optimization (The user vsetvls should be
+                 on the optimal local already before this pass)
+                 again for user vsetvls in VSETVL PASS here
+                 (Phase 3 && Phase 4).
+
+               - Allowing user vsetvls be optimized in PRE
+                 optimization here (Phase 3 && Phase 4) will
+                 complicate the codes so much so we prefer user
+                 vsetvls be optimized in post-optimization
+                 (Phase 5 && Phase 6).  */
+             if (vsetvl_insn_p (expr.get_insn ()->rtl ()))
+               {
+                 if (src_block_info.reaching_out.empty_p ())
+                   continue;
+                 else if (src_block_info.reaching_out.dirty_p ()
+                          && !src_block_info.reaching_out.compatible_p (expr))
+                   {
+                     new_info.set_empty ();
+                     /* Update probability as uninitialized status so that
+                        we won't try to fuse any demand info into such EMPTY
+                        block any more.  */
+                     prob = profile_probability::uninitialized ();
+                     update_block_info (eg->src->index, prob, new_info);
+                     continue;
+                   }
+               }
 
              if (src_block_info.reaching_out.empty_p ())
                {
                  if (src_block_info.probability
-                       == profile_probability::uninitialized ()
-                     || vsetvl_insn_p (expr.get_insn ()->rtl ()))
+                     == profile_probability::uninitialized ())
                    continue;
                  new_info = expr.global_merge (expr, eg->src->index);
                  new_info.set_dirty ();