Optimize ashift >> 7 to vpcmpgtb for vector int8.

Since there is no corresponding instruction, the shift operation for
vector int8 is implemented using the instructions for vector int16,
but for some special shift counts, it can be transformed into vpcmpgtb.

gcc/ChangeLog:

	PR target/114514
	* config/i386/i386-expand.cc
	(ix86_expand_vec_shift_qihi_constant): Optimize ashift >> 7 to
	vpcmpgtb.
	(ix86_expand_vecop_qihi_partial): Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr114514-shift.c: New test.

2 files changed, 81 insertions, 0 deletions

diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
index e846a94..4c47cfe 100644
--- a/gcc/config/i386/i386-expand.cc
+++ b/gcc/config/i386/i386-expand.cc
@@ -24246,6 +24246,28 @@ ix86_expand_vec_shift_qihi_constant (enum rtx_code code,
     return false;
 
   gcc_assert (code == ASHIFT || code == ASHIFTRT || code == LSHIFTRT);
+
+
+  if (shift_amount == 7
+      && code == ASHIFTRT)
+    {
+      if (qimode == V16QImode
+	  || qimode == V32QImode)
+	{
+	  rtx zero = gen_reg_rtx (qimode);
+	  emit_move_insn (zero, CONST0_RTX (qimode));
+	  emit_move_insn (dest, gen_rtx_fmt_ee (GT, qimode, zero, op1));
+	}
+      else
+	{
+	  gcc_assert (qimode == V64QImode);
+	  rtx kmask = gen_reg_rtx (DImode);
+	  emit_insn (gen_avx512bw_cvtb2maskv64qi (kmask, op1));
+	  emit_insn (gen_avx512bw_cvtmask2bv64qi (dest, kmask));
+	}
+      return true;
+    }
+
   /* Record sign bit.  */
   xor_constant = 1 << (8 - shift_amount - 1);
 
@@ -24356,6 +24378,16 @@ ix86_expand_vecop_qihi_partial (enum rtx_code code, rtx dest, rtx op1, rtx op2)
       return;
     }
 
+  if (CONST_INT_P (op2)
+      && code == ASHIFTRT
+      && INTVAL (op2) == 7)
+    {
+      rtx zero = gen_reg_rtx (qimode);
+      emit_move_insn (zero, CONST0_RTX (qimode));
+      emit_move_insn (dest, gen_rtx_fmt_ee (GT, qimode, zero, op1));
+      return;
+    }
+
   switch (code)
     {
     case MULT:
diff --git a/gcc/testsuite/gcc.target/i386/pr114514-shift.c b/gcc/testsuite/gcc.target/i386/pr114514-shift.c
new file mode 100644
index 0000000..cf8b32b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr114514-shift.c
@@ -0,0 +1,49 @@
+/* { dg-do compile  } */
+/* { dg-options "-mavx512vl -mavx512bw -O2" } */
+/* { dg-final { scan-assembler-times "vpxor" 4 } } */
+/* { dg-final { scan-assembler-times "vpcmpgtb" 4 { target { ! ia32 } } } } */
+/* { dg-final { scan-assembler-times "vpcmpgtb" 5 { target  ia32 } } } */
+/* { dg-final { scan-assembler-times "vpmovb2m" 1 } } */
+/* { dg-final { scan-assembler-times "vpmovm2b" 1 } } */
+
+
+typedef char v16qi __attribute__((vector_size(16)));
+typedef char v32qi __attribute__((vector_size(32)));
+typedef char v64qi __attribute__((vector_size(64)));
+typedef char v8qi __attribute__((vector_size(8)));
+typedef char v4qi __attribute__((vector_size(4)));
+
+v4qi
+__attribute__((noipa))
+foo1 (v4qi a)
+{
+  return a >> 7;
+}
+
+v8qi
+__attribute__((noipa))
+foo2 (v8qi a)
+{
+  return a >> 7;
+}
+
+v16qi
+__attribute__((noipa))
+foo3 (v16qi a)
+{
+  return a >> 7;
+}
+
+v32qi
+__attribute__((noipa))
+foo4 (v32qi a)
+{
+  return a >> 7;
+}
+
+v64qi
+__attribute__((noipa))
+foo5 (v64qi a)
+{
+  return a >> 7;
+}