arm: Implement MVE predicates as vectors of booleans

This patch implements support for vectors of booleans to support MVE
predicates, instead of HImode.  Since the ABI mandates pred16_t (aka
uint16_t) to represent predicates in intrinsics prototypes, we
introduce a new "predicate" type qualifier so that we can map relevant
builtins HImode arguments and return value to the appropriate vector
of booleans (VxBI).

We have to update test_vector_ops_duplicate, because it iterates using
an offset in bytes, where we would need to iterate in bits: we stop
iterating when we reach the end of the vector of booleans.

In addition, we have to fix the underlying definition of vectors of
booleans because ARM/MVE needs a different representation than
AArch64/SVE. With ARM/MVE the 'true' bit is duplicated over the
element size, so that a true element of V4BI is represented by
'0b1111'.  This patch updates the aarch64 definition of VNx*BI as
needed.

Most of the work of this patch series was carried out while I was
working at STMicroelectronics as a Linaro assignee.

2022-02-22  Christophe Lyon  <christophe.lyon@arm.com>
	    Richard Sandiford  <richard.sandiford@arm.com>

	gcc/
	PR target/100757
	PR target/101325
	* config/aarch64/aarch64-modes.def (VNx16BI, VNx8BI, VNx4BI,
	VNx2BI): Update definition.
	* config/arm/arm-builtins.cc (arm_init_simd_builtin_types): Add new
	simd types.
	(arm_init_builtin): Map predicate vectors arguments to HImode.
	(arm_expand_builtin_args): Move HImode predicate arguments to VxBI
	rtx. Move return value to HImode rtx.
	* config/arm/arm-builtins.h (arm_type_qualifiers): Add qualifier_predicate.
	* config/arm/arm-modes.def (B2I, B4I, V16BI, V8BI, V4BI): New modes.
	* config/arm/arm-simd-builtin-types.def (Pred1x16_t,
	Pred2x8_t,Pred4x4_t): New.
	* emit-rtl.cc (init_emit_once): Handle all boolean modes.
	* genmodes.cc (mode_data): Add boolean field.
	(blank_mode): Initialize it.
	(make_complex_modes): Fix handling of boolean modes.
	(make_vector_modes): Likewise.
	(VECTOR_BOOL_MODE): Use new COMPONENT parameter.
	(make_vector_bool_mode): Likewise.
	(BOOL_MODE): New.
	(make_bool_mode): New.
	(emit_insn_modes_h): Fix generation of boolean modes.
	(emit_class_narrowest_mode): Likewise.
	* machmode.def: (VECTOR_BOOL_MODE): Document new COMPONENT
	parameter.  Use new BOOL_MODE instead of FRACTIONAL_INT_MODE to
	define BImode.
	* rtx-vector-builder.cc (rtx_vector_builder::find_cached_value):
	Fix handling of constm1_rtx for VECTOR_BOOL.
	* simplify-rtx.cc (native_encode_rtx): Fix support for VECTOR_BOOL.
	(native_decode_vector_rtx): Likewise.
	(test_vector_ops_duplicate): Skip vec_merge test
	with vectors of booleans.
	* varasm.cc (output_constant_pool_2): Likewise.

1 files changed, 22 insertions, 6 deletions

diff --git a/gcc/emit-rtl.cc b/gcc/emit-rtl.cc
index a26bcb0..f4404d7 100644
--- a/gcc/emit-rtl.cc
+++ b/gcc/emit-rtl.cc
@@ -6239,9 +6239,22 @@ init_emit_once (void)
 
   /* For BImode, 1 and -1 are unsigned and signed interpretations
      of the same value.  */
-  const_tiny_rtx[0][(int) BImode] = const0_rtx;
-  const_tiny_rtx[1][(int) BImode] = const_true_rtx;
-  const_tiny_rtx[3][(int) BImode] = const_true_rtx;
+  for (mode = MIN_MODE_BOOL;
+       mode <= MAX_MODE_BOOL;
+       mode = (machine_mode)((int)(mode) + 1))
+    {
+      const_tiny_rtx[0][(int) mode] = const0_rtx;
+      if (mode == BImode)
+	{
+	  const_tiny_rtx[1][(int) mode] = const_true_rtx;
+	  const_tiny_rtx[3][(int) mode] = const_true_rtx;
+	}
+      else
+	{
+	  const_tiny_rtx[1][(int) mode] = const1_rtx;
+	  const_tiny_rtx[3][(int) mode] = constm1_rtx;
+	}
+    }
 
   for (mode = MIN_MODE_PARTIAL_INT;
        mode <= MAX_MODE_PARTIAL_INT;
@@ -6260,13 +6273,16 @@ init_emit_once (void)
       const_tiny_rtx[0][(int) mode] = gen_rtx_CONCAT (mode, inner, inner);
     }
 
-  /* As for BImode, "all 1" and "all -1" are unsigned and signed
-     interpretations of the same value.  */
   FOR_EACH_MODE_IN_CLASS (mode, MODE_VECTOR_BOOL)
     {
       const_tiny_rtx[0][(int) mode] = gen_const_vector (mode, 0);
       const_tiny_rtx[3][(int) mode] = gen_const_vector (mode, 3);
-      const_tiny_rtx[1][(int) mode] = const_tiny_rtx[3][(int) mode];
+      if (GET_MODE_INNER (mode) == BImode)
+	/* As for BImode, "all 1" and "all -1" are unsigned and signed
+	   interpretations of the same value.  */
+	const_tiny_rtx[1][(int) mode] = const_tiny_rtx[3][(int) mode];
+      else
+	const_tiny_rtx[1][(int) mode] = gen_const_vector (mode, 1);
     }
 
   FOR_EACH_MODE_IN_CLASS (mode, MODE_VECTOR_INT)