RISC-V: vsetvl: elide abnormal edges from LCM computations [PR119533]

vsetvl phase4 uses LCM guided info to insert VSETVL insns, including a
straggler loop for "mising vsetvls" on certain edges. Currently it
asserts on encountering EDGE_ABNORMAL.

When enabling go frontend with V enabled, libgo build hits the assert.

The solution is to prevent abnormal edges from getting into LCM at all
(my prior attempt at this just ignored them after LCM which is not
right). Existing invalid_opt_bb_p () current does this for BB predecessors
but not for successors which is what the patch adds.

Crucially, the ICE/fix also depends on avoiding vsetvl hoisting past
non-transparent blocks: That is taken care of by Robin's patch
"RISC-V: Do not lift up vsetvl into non-transparent blocks [PR119547]"
for a different yet related issue.

Reported-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>

	PR target/119533

gcc/ChangeLog:

	* config/riscv/riscv-vsetvl.cc (invalid_opt_bb_p): Check for
	EDGE_ABNOMAL.
	(pre_vsetvl::compute_lcm_local_properties): Initialize kill
	bitmap.
	Debug dump skipped edge.

gcc/testsuite/ChangeLog:

	* go.dg/pr119533-riscv.go: New test.
	* go.dg/pr119533-riscv-2.go: New test.

3 files changed, 168 insertions, 1 deletions

diff --git a/gcc/config/riscv/riscv-vsetvl.cc b/gcc/config/riscv/riscv-vsetvl.cc
index c4046bc..a8c9256 100644
--- a/gcc/config/riscv/riscv-vsetvl.cc
+++ b/gcc/config/riscv/riscv-vsetvl.cc
@@ -685,7 +685,7 @@ invalid_opt_bb_p (basic_block cfg_bb)
   /* We only do LCM optimizations on blocks that are post dominated by
      EXIT block, that is, we don't do LCM optimizations on infinite loop.  */
   FOR_EACH_EDGE (e, ei, cfg_bb->succs)
-    if (e->flags & EDGE_FAKE)
+    if ((e->flags & EDGE_FAKE) || (e->flags & EDGE_ABNORMAL))
       return true;
 
   return false;
@@ -2698,6 +2698,7 @@ pre_vsetvl::compute_lcm_local_properties ()
   m_avout = sbitmap_vector_alloc (last_basic_block_for_fn (cfun), num_exprs);
 
   bitmap_vector_clear (m_avloc, last_basic_block_for_fn (cfun));
+  bitmap_vector_clear (m_kill, last_basic_block_for_fn (cfun));
   bitmap_vector_clear (m_antloc, last_basic_block_for_fn (cfun));
   bitmap_vector_ones (m_transp, last_basic_block_for_fn (cfun));
 
@@ -2749,6 +2750,10 @@ pre_vsetvl::compute_lcm_local_properties ()
 
       if (invalid_opt_bb_p (bb->cfg_bb ()))
 	{
+	  if (dump_file && (dump_flags & TDF_DETAILS))
+	    fprintf (dump_file, "\n --- skipping bb %u due to weird edge",
+		     bb->index ());
+
 	  bitmap_clear (m_antloc[bb_index]);
 	  bitmap_clear (m_transp[bb_index]);
 	}
diff --git a/gcc/testsuite/go.dg/pr119533-riscv-2.go b/gcc/testsuite/go.dg/pr119533-riscv-2.go
new file mode 100644
index 0000000..ce3ffaf
--- /dev/null
+++ b/gcc/testsuite/go.dg/pr119533-riscv-2.go
@@ -0,0 +1,42 @@
+// { dg-do compile { target riscv64*-*-* } }
+// { dg-options "-O2 -march=rv64gcv -mabi=lp64d" }
+
+package ast
+
+type as struct {
+	bt []struct{}
+	an string
+}
+
+func bj(a *as) string {
+	if b := a.bt; len(a.an) == 1 {
+		_ = b[0]
+	}
+	return a.an
+}
+
+func MergePackageFiles(f map[string][]interface{}, g uint) []interface{} {
+	bl := make([]string, len(f))
+	var bo []interface{}
+	bu := make(map[string]int)
+	for _, bm := range bl {
+		a := f[bm]
+		for _, d := range a {
+			if g != 0 {
+				if a, p := d.(*as); p {
+					n := bj(a)
+					if j, bp := bu[n]; bp {
+						_ = j
+					}
+				}
+			}
+		}
+	}
+	for _, bm := range bl {
+		_ = bm
+	}
+	for _, bm := range bl {
+		_ = f[bm]
+	}
+	return bo
+}
diff --git a/gcc/testsuite/go.dg/pr119533-riscv.go b/gcc/testsuite/go.dg/pr119533-riscv.go
new file mode 100644
index 0000000..30f52d2
--- /dev/null
+++ b/gcc/testsuite/go.dg/pr119533-riscv.go
@@ -0,0 +1,120 @@
+// { dg-do compile { target riscv64*-*-* } }
+// { dg-options "-O2 -march=rv64gcv -mabi=lp64d" }
+
+// Reduced from libgo build (multi-file reduction, merged mnaully
+// and hand reduced again).
+
+package ast
+import (
+	"go/token"
+	"go/scanner"
+	"reflect"
+)
+type v struct {}
+type w func( string,  reflect.Value) bool
+func x( string,  reflect.Value) bool
+type r struct {
+	scanner.ErrorList
+}
+type ab interface {}
+type ae interface {}
+type af interface {}
+type ag struct {}
+func (ag) Pos() token.Pos
+func (ag) ah() token.Pos
+type c struct {
+	aj    ae          }
+type ak struct {
+	al    []c  }
+type (
+	am struct {
+		an    string    }
+	bs struct {
+		Value    string
+	  }
+)
+func ao(string) *am
+type (
+	ap interface {}
+	aq struct {
+		ar    bs     }
+as struct {
+		bt ak
+		an am        }
+)
+type File struct {
+	*ag
+	token.Pos
+	*am
+	at      []af
+	*v
+	au    []*aq
+	av *am
+	aw   []*ag }
+type ax struct {
+	an    string
+	*v
+	ay   map[string]File   }
+func a(az *token.FileSet, b token.Pos) int
+type k struct {
+	l token.Pos
+	ah   token.Pos
+}
+type m struct {
+	bb bool
+	bc   *ag
+}
+
+type bi uint
+func bj(a *as) string {
+	if b := a.bt; len(b.al) == 1 {
+		c := b.al[0].aj
+		if e := c; e != nil {}
+	}
+	return a.an.an
+}
+func MergePackageFiles(f ax, g bi) *File {
+	h := 0
+	bk := 0
+	k := 0
+	bl := make([]string, len(f.ay))
+	i := 0
+	for bm, a := range f.ay {
+		bl[i] = bm
+		k += len(a.at)
+	}
+	var bn *ag
+	var l token.Pos
+	if h > 0 {}
+	var bo []af
+		bu := make(map[string]int)
+		m := 0
+		for _, bm := range bl {
+			a := f.ay[bm]
+			for _, d := range a.at {
+				if g!= 0 {
+					if a, p := d.(*as); p {
+						n := bj(a)
+						if j, bp := bu[n]; bp {
+							if bo != nil && bo[j]== nil {}
+						}
+					}
+				}
+			}
+		}
+		if m > 0 {}
+	var bq []*aq
+		q := make(map[string]bool)
+		for _, bm := range bl {
+			a := f.ay[bm]
+			for _, br := range a.au {
+				if o := br.ar.Value; q[o] {}
+			}
+		}
+	var bh = make([]*ag, bk)
+		for _, bm := range bl {
+			a := f.ay[bm]
+			copy(bh, a.aw)
+		}
+	return &File{bn, l, ao(f.an), bo, f.v, bq, nil, bh}
+}