[gcc r14-5507] RISC-V: fix vsetvli pass testsuite failure [PR/112447]

[gcc r14-5507] RISC-V: fix vsetvli pass testsuite failure [PR/112447]

[Vineet Gupta]

https://gcc.gnu.org/g:d1189ceefc1da1515e039c9cfd2f5a67b5820207

commit r14-5507-gd1189ceefc1da1515e039c9cfd2f5a67b5820207
Author: Juzhe-Zhong <juzhe.zhong@rivai.ai>
Date:   Tue Nov 14 19:23:19 2023 -0800

    RISC-V: fix vsetvli pass testsuite failure [PR/112447]
    
    Fixes: f0e28d8c1371 ("RISC-V: Fix failed hoist in LICM of vmv.v.x instruction")
    
    Since above commit, we have following failure:
    
      FAIL: gcc.c-torture/execute/memset-3.c   -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions execution test
      FAIL: gcc.c-torture/execute/memset-3.c   -O3 -g  execution test
    
    The issue was not the commit but rather it unravelled an issue in the
    vsetvli pass.
    
    Here's Juzhe's analysis:
    
    We have 2 types of global vsetvls insertion.
    One is earliest fusion of each end of the block.
    The other is LCM suggested edge vsetvls.
    
    So before this patch, insertion as follows:
    
    |  (insn 2817 2820 2818 361 (set (reg:SI 67 vtype)
    |        (unspec:SI [
    |                (const_int 8 [0x8])
    |                (const_int 7 [0x7])
    |                (const_int 1 [0x1]) repeated x2
    |            ] UNSPEC_VSETVL)) 1708 {vsetvl_vtype_change_only}
    |     (nil))
    |  (insn 2818 2817 999 361 (set (reg:SI 67 vtype)
    |        (unspec:SI [
    |                (const_int 32 [0x20])
    |                (const_int 1 [0x1]) repeated x3
    |            ] UNSPEC_VSETVL)) 1708 {vsetvl_vtype_change_only}
    |     (nil))
    
    After this patch:
    
    |  (insn 2817 2820 2819 361 (set (reg:SI 67 vtype)
    |        (unspec:SI [
    |                (const_int 32 [0x20])
    |                (const_int 1 [0x1]) repeated x3
    |            ] UNSPEC_VSETVL)) 1708 {vsetvl_vtype_change_only}
    |     (nil))
    |  (insn 2819 2817 999 361 (set (reg:SI 67 vtype)
    |        (unspec:SI [
    |                (const_int 8 [0x8])
    |                (const_int 7 [0x7])
    |                (const_int 1 [0x1]) repeated x2
    |            ] UNSPEC_VSETVL)) 1708 {vsetvl_vtype_change_only}
    |     (nil))
    
    The original insertion order is incorrect.
    
    We should first insert earliest fusion since it is the vsetvls information
    already there which was seen by later LCM. We just delay the insertion.
    So it should be come before the LCM suggested insertion.
    
            PR target/112447
    
    gcc/ChangeLog:
            * config/riscv/riscv-vsetvl.cc (pre_vsetvl::emit_vsetvl): Insert
            local vsetvl info before LCM suggested one.
    
            Tested-by: Patrick O'Neill <patrick@rivosinc.com> # pre-commit-CI #679
            Co-developed-by: Vineet Gupta <vineetg@rivosinc.com>

Diff:
---
 gcc/config/riscv/riscv-vsetvl.cc | 70 ++++++++++++++++++++--------------------
 1 file changed, 35 insertions(+), 35 deletions(-)

diff --git a/gcc/config/riscv/riscv-vsetvl.cc b/gcc/config/riscv/riscv-vsetvl.cc
index 8466b5d019e..74367ec8d8e 100644
--- a/gcc/config/riscv/riscv-vsetvl.cc
+++ b/gcc/config/riscv/riscv-vsetvl.cc
@@ -3229,6 +3229,41 @@ pre_vsetvl::emit_vsetvl ()
       remove_vsetvl_insn (item);
     }
 
+  /* Insert vsetvl info that was not deleted after lift up.  */
+  for (const bb_info *bb : crtl->ssa->bbs ())
+    {
+      const vsetvl_block_info &block_info = get_block_info (bb);
+      if (!block_info.has_info ())
+	continue;
+
+      const vsetvl_info &footer_info = block_info.get_exit_info ();
+
+      if (footer_info.delete_p ())
+	continue;
+
+      edge eg;
+      edge_iterator eg_iterator;
+      FOR_EACH_EDGE (eg, eg_iterator, bb->cfg_bb ()->succs)
+	{
+	  gcc_assert (!(eg->flags & EDGE_ABNORMAL));
+	  if (dump_file)
+	    {
+	      fprintf (
+		dump_file,
+		"\n  Insert missed vsetvl info at edge(bb %u -> bb %u): ",
+		eg->src->index, eg->dest->index);
+	      footer_info.dump (dump_file, "    ");
+	    }
+	  start_sequence ();
+	  insert_vsetvl_insn (EMIT_DIRECT, footer_info);
+	  rtx_insn *rinsn = get_insns ();
+	  end_sequence ();
+	  default_rtl_profile ();
+	  insert_insn_on_edge (rinsn, eg);
+	  need_commit = true;
+	}
+    }
+
   /* m_insert vsetvl as LCM suggest. */
   for (int ed = 0; ed < NUM_EDGES (m_edges); ed++)
     {
@@ -3267,41 +3302,6 @@ pre_vsetvl::emit_vsetvl ()
       insert_insn_on_edge (rinsn, eg);
     }
 
-  /* Insert vsetvl info that was not deleted after lift up.  */
-  for (const bb_info *bb : crtl->ssa->bbs ())
-    {
-      const vsetvl_block_info &block_info = get_block_info (bb);
-      if (!block_info.has_info ())
-	continue;
-
-      const vsetvl_info &footer_info = block_info.get_exit_info ();
-
-      if (footer_info.delete_p ())
-	continue;
-
-      edge eg;
-      edge_iterator eg_iterator;
-      FOR_EACH_EDGE (eg, eg_iterator, bb->cfg_bb ()->succs)
-	{
-	  gcc_assert (!(eg->flags & EDGE_ABNORMAL));
-	  if (dump_file)
-	    {
-	      fprintf (
-		dump_file,
-		"\n  Insert missed vsetvl info at edge(bb %u -> bb %u): ",
-		eg->src->index, eg->dest->index);
-	      footer_info.dump (dump_file, "    ");
-	    }
-	  start_sequence ();
-	  insert_vsetvl_insn (EMIT_DIRECT, footer_info);
-	  rtx_insn *rinsn = get_insns ();
-	  end_sequence ();
-	  default_rtl_profile ();
-	  insert_insn_on_edge (rinsn, eg);
-	  need_commit = true;
-	}
-    }
-
   if (need_commit)
     commit_edge_insertions ();
 }