RISC-V: Fix PR109615

This patch is to fix following case:
void f (int8_t * restrict in, int8_t * restrict out, int n, int m, int cond)
{
  size_t vl = 101;
  if (cond)
    vl = m * 2;
  else
    vl = m * 2 * vl;

  for (size_t i = 0; i < n; i++)
    {
      vint8mf8_t v = __riscv_vle8_v_i8mf8 (in + i, vl);
      __riscv_vse8_v_i8mf8 (out + i, v, vl);

      vbool64_t mask = __riscv_vlm_v_b64 (in + i + 100, vl);

      vint8mf8_t v2 = __riscv_vle8_v_i8mf8_tumu (mask, v, in + i + 100, vl);
      __riscv_vse8_v_i8mf8 (out + i + 100, v2, vl);
    }

  for (size_t i = 0; i < n; i++)
    {
      vint8mf8_t v = __riscv_vle8_v_i8mf8 (in + i + 300, vl);
      __riscv_vse8_v_i8mf8 (out + i + 300, v, vl);
    }
}

The value of "vl" is coming from different blocks so it will be wrapped as a PHI node of each
block.

In the first loop, the "vl" source is a PHI node from bb 4.
In the second loop, the "vl" source is a PHI node from bb 5.
since bb 5 is dominated by bb 4, the PHI input of "vl" in the second loop is the PHI node of "vl"
in bb 4.
So when 2 "vl" PHI node are both degenerate PHI node (the phi->num_inputs () == 1) and their only
input are same, it's safe for us to consider they are compatible.

This patch is only optimize degenerate PHI since it's safe and simple optimization.

non-dengerate PHI are considered as incompatible unless the PHI are the same in RTL_SSA.
TODO: non-generate PHI is complicated, we can support it when it is necessary in the future.

Before this patch:

...
.L2:
	addi    a4,a1,100
	add     t1,a0,a2
	mv      t0,a0
	beq     a2,zero,.L1
	vsetvli zero,a3,e8,mf8,tu,mu
.L4:
	addi    a6,t0,100
	addi    a7,a4,-100
	vle8.v  v1,0(t0)
	addi    t0,t0,1
	vse8.v  v1,0(a7)
	vlm.v   v0,0(a6)
	vle8.v  v1,0(a6),v0.t
	vse8.v  v1,0(a4)
	addi    a4,a4,1
	bne     t0,t1,.L4
	addi    a0,a0,300
	addi    a1,a1,300
	add     a2,a0,a2
	vsetvli zero,a3,e8,mf8,ta,ma
.L5:
	vle8.v  v2,0(a0)
	addi    a0,a0,1
	vse8.v  v2,0(a1)
	addi    a1,a1,1
	bne     a2,a0,.L5
.L1:
	ret

After this patch:

...
.L2:
	addi    a4,a1,100
	add     t1,a0,a2
	mv      t0,a0
	beq     a2,zero,.L1
	vsetvli zero,a3,e8,mf8,tu,mu
.L4:
	addi    a6,t0,100
	addi    a7,a4,-100
	vle8.v  v1,0(t0)
	addi    t0,t0,1
	vse8.v  v1,0(a7)
	vlm.v   v0,0(a6)
	vle8.v  v1,0(a6),v0.t
	vse8.v  v1,0(a4)
	addi    a4,a4,1
	bne     t0,t1,.L4
	addi    a0,a0,300
	addi    a1,a1,300
	add     a2,a0,a2
.L5:
	vle8.v  v2,0(a0)
	addi    a0,a0,1
	vse8.v  v2,0(a1)
	addi    a1,a1,1
	bne     a2,a0,.L5
.L1:
	ret

	PR target/109615

gcc/ChangeLog:

	* config/riscv/riscv-vsetvl.cc (avl_info::multiple_source_equal_p): Add
	denegrate PHI optmization.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/vsetvl/avl_single-74.c: Adapt testcase.
	* gcc.target/riscv/rvv/vsetvl/vsetvl-11.c: Ditto.
	* gcc.target/riscv/rvv/vsetvl/pr109615.c: New test.

4 files changed, 56 insertions, 66 deletions

diff --git a/gcc/config/riscv/riscv-vsetvl.cc b/gcc/config/riscv/riscv-vsetvl.cc
index 609f86d..b9172e5 100644
--- a/gcc/config/riscv/riscv-vsetvl.cc
+++ b/gcc/config/riscv/riscv-vsetvl.cc
@@ -1676,72 +1676,29 @@ avl_info::single_source_equal_p (const avl_info &other) const
 bool
 avl_info::multiple_source_equal_p (const avl_info &other) const
 {
-  /* TODO: We don't do too much optimization here since it's
-     too complicated in case of analyzing the PHI node.
+  /* When the def info is same in RTL_SSA namespace, it's safe
+     to consider they are avl compatible.  */
+  if (m_source == other.get_source ())
+    return true;
 
-     For example:
-       void f (void * restrict in, void * restrict out, int n, int m, int cond)
-	{
-	  size_t vl;
-	  switch (cond)
-	  {
-	  case 1:
-	    vl = 100;
-	    break;
-	  case 2:
-	    vl = *(size_t*)(in + 100);
-	    break;
-	  case 3:
-	    {
-	      size_t new_vl = *(size_t*)(in + 500);
-	      size_t new_vl2 = *(size_t*)(in + 600);
-	      vl = new_vl + new_vl2 + 777;
-	      break;
-	    }
-	  default:
-	    vl = 4000;
-	    break;
-	  }
-	  for (size_t i = 0; i < n; i++)
-	    {
-	      vint8mf8_t v = __riscv_vle8_v_i8mf8 (in + i, vl);
-	      __riscv_vse8_v_i8mf8 (out + i, v, vl);
+  /* We only consider handle PHI node.  */
+  if (!m_source->insn ()->is_phi () || !other.get_source ()->insn ()->is_phi ())
+    return false;
 
-	      vint8mf8_t v2 = __riscv_vle8_v_i8mf8_tu (v, in + i + 100, vl);
-	      __riscv_vse8_v_i8mf8 (out + i + 100, v2, vl);
-	    }
+  phi_info *phi1 = as_a<phi_info *> (m_source);
+  phi_info *phi2 = as_a<phi_info *> (other.get_source ());
 
-	  size_t vl2;
-	  switch (cond)
-	  {
-	  case 1:
-	    vl2 = 100;
-	    break;
-	  case 2:
-	    vl2 = *(size_t*)(in + 100);
-	    break;
-	  case 3:
-	    {
-	      size_t new_vl = *(size_t*)(in + 500);
-	      size_t new_vl2 = *(size_t*)(in + 600);
-	      vl2 = new_vl + new_vl2 + 777;
-	      break;
-	    }
-	  default:
-	    vl2 = 4000;
-	    break;
-	  }
-	  for (size_t i = 0; i < m; i++)
-	    {
-	      vint8mf8_t v = __riscv_vle8_v_i8mf8 (in + i + 300, vl2);
-	      __riscv_vse8_v_i8mf8 (out + i + 300, v, vl2);
-	      vint8mf8_t v2 = __riscv_vle8_v_i8mf8_tu (v, in + i + 200, vl2);
-	      __riscv_vse8_v_i8mf8 (out + i + 200, v2, vl2);
-	    }
-	}
-     Such case may not be necessary to optimize since the codes of defining
-     vl and vl2 are redundant.  */
-  return m_source == other.get_source ();
+  if (phi1->is_degenerate () && phi2->is_degenerate ())
+    {
+      /* Degenerate PHI means the PHI node only have one input.  */
+
+      /* If both PHI nodes have the same single input in use list.
+	 We consider they are AVL compatible.  */
+      if (phi1->input_value (0) == phi2->input_value (0))
+	return true;
+    }
+  /* TODO: We can support more optimization cases in the future.  */
+  return false;
 }
 
 avl_info &
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/avl_single-74.c b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/avl_single-74.c
index ff540ec..cc4f88b 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/avl_single-74.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/avl_single-74.c
@@ -23,5 +23,5 @@ void f (int8_t * restrict in, int8_t * restrict out, int n, int cond, size_t vl,
     }
 }
 
-/* { dg-final { scan-assembler-times {vsetvli\s+zero,\s*[a-x0-9]+,\s*e8,\s*mf8,\s*t[au],\s*m[au]} 2 { target { no-opts "-O0" no-opts "-O1" no-opts "-Os" no-opts "-Oz" no-opts "-g" no-opts "-funroll-loops" } } } } */
-/* { dg-final { scan-assembler-times {vsetvli} 2 { target { no-opts "-O0" no-opts "-O1" no-opts "-Os" no-opts "-Oz" no-opts "-g" no-opts "-funroll-loops" } } } } */
+/* { dg-final { scan-assembler-times {vsetvli\s+zero,\s*[a-x0-9]+,\s*e8,\s*mf8,\s*tu,\s*m[au]} 1 { target { no-opts "-O0" no-opts "-O1" no-opts "-Os" no-opts "-Oz" no-opts "-g" no-opts "-funroll-loops" } } } } */
+/* { dg-final { scan-assembler-times {vsetvli} 1 { target { no-opts "-O0" no-opts "-O1" no-opts "-Os" no-opts "-Oz" no-opts "-g" no-opts "-funroll-loops" } } } } */
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/pr109615.c b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/pr109615.c
new file mode 100644
index 0000000..90b0bb7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/pr109615.c
@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv32gcv -mabi=ilp32 -fno-tree-vectorize -fno-schedule-insns -fno-schedule-insns2" } */
+
+#include "riscv_vector.h"
+
+void f (int8_t * restrict in, int8_t * restrict out, int n, int m, int cond)
+{
+  size_t vl = 101;
+  if (cond)
+    vl = m * 2;
+  else
+    vl = m * 2 * vl;
+
+  for (size_t i = 0; i < n; i++)
+    {
+      vint8mf8_t v = __riscv_vle8_v_i8mf8 (in + i, vl);
+      __riscv_vse8_v_i8mf8 (out + i, v, vl);
+
+      vbool64_t mask = __riscv_vlm_v_b64 (in + i + 100, vl);
+
+      vint8mf8_t v2 = __riscv_vle8_v_i8mf8_tumu (mask, v, in + i + 100, vl);
+      __riscv_vse8_v_i8mf8 (out + i + 100, v2, vl);
+    }
+
+  for (size_t i = 0; i < n; i++)
+    {
+      vint8mf8_t v = __riscv_vle8_v_i8mf8 (in + i + 300, vl);
+      __riscv_vse8_v_i8mf8 (out + i + 300, v, vl);
+    }
+}
+
+/* { dg-final { scan-assembler-times {vsetvli\s+zero,\s*[a-x0-9]+,\s*e8,\s*mf8,\s*tu,\s*mu} 1 { target { no-opts "-O0" no-opts "-O1" no-opts "-Os" no-opts "-Oz" no-opts "-g" no-opts "-funroll-loops" } } } } */
+/* { dg-final { scan-assembler-times {vsetvli} 1 { target { no-opts "-O0" no-opts "-O1" no-opts "-Os" no-opts "-Oz" no-opts "-g" no-opts "-funroll-loops" } } } } */
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/vsetvl-11.c b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/vsetvl-11.c
index fa825f0..3ef0fdc 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/vsetvl-11.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/vsetvl-11.c
@@ -18,4 +18,4 @@ void foo(int32_t *in1, int32_t *in2, int32_t *in3, int32_t *out, size_t n, int c
   }
 }
 
-/* { dg-final { scan-assembler-times {vsetvli} 3 { target { no-opts "-O0" no-opts "-g" no-opts "-funroll-loops" } } } } */
+/* { dg-final { scan-assembler-times {vsetvli} 2 { target { no-opts "-O0" no-opts "-g" no-opts "-funroll-loops" } } } } */