gcc: Add vec_select -> subreg RTL simplification

Add a new RTL simplification for the case of a VEC_SELECT selecting
the low part of a vector. The simplification returns a SUBREG.

The primary goal of this patch is to enable better combinations of
Neon RTL patterns - specifically allowing generation of 'write-to-
high-half' narrowing intructions.

Adding this RTL simplification means that the expected results for a
number of tests need to be updated:
* aarch64 Neon: Update the scan-assembler regex for intrinsics tests
  to expect a scalar register instead of lane 0 of a vector.
* aarch64 SVE: Likewise.
* arm MVE: Use lane 1 instead of lane 0 for lane-extraction
  intrinsics tests (as the move instructions get optimized away for
  lane 0.)

This patch also adds new code generation tests to
narrow_high_combine.c to verify the benefit of this RTL
simplification.

gcc/ChangeLog:

2021-06-08  Jonathan Wright  <jonathan.wright@arm.com>

	* combine.c (combine_simplify_rtx): Add vec_select -> subreg
	simplification.
	* config/aarch64/aarch64.md (*zero_extend<SHORT:mode><GPI:mode>2_aarch64):
	Add Neon to general purpose register case for zero-extend
	pattern.
	* config/arm/vfp.md (*arm_movsi_vfp): Remove "*" from *t -> r
	case to prevent some cases opting to go through memory.
	* cse.c (fold_rtx): Add vec_select -> subreg simplification.
	* rtl.c (rtvec_series_p): Define predicate to determine
	whether a vector contains a linear series of integers.
	* rtl.h (rtvec_series_p): Define.
	* rtlanal.c (vec_series_lowpart_p): Define predicate to
	determine if a vector selection is equivalent to the low part
	of the vector.
	* rtlanal.h (vec_series_lowpart_p): Define.
	* simplify-rtx.c (simplify_context::simplify_binary_operation_1):
	Add vec_select -> subreg simplification.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/extract_zero_extend.c: Remove dump scan
	for RTL pattern match.
	* gcc.target/aarch64/narrow_high_combine.c: Add new tests.
	* gcc.target/aarch64/simd/vmulx_laneq_f64_1.c: Update
	scan-assembler regex to look for a scalar register instead of
	lane 0 of a vector.
	* gcc.target/aarch64/simd/vmulxd_laneq_f64_1.c: Likewise.
	* gcc.target/aarch64/simd/vmulxs_lane_f32_1.c: Likewise.
	* gcc.target/aarch64/simd/vmulxs_laneq_f32_1.c: Likewise.
	* gcc.target/aarch64/simd/vqdmlalh_lane_s16.c: Likewise.
	* gcc.target/aarch64/simd/vqdmlals_lane_s32.c: Likewise.
	* gcc.target/aarch64/simd/vqdmlslh_lane_s16.c: Likewise.
	* gcc.target/aarch64/simd/vqdmlsls_lane_s32.c: Likewise.
	* gcc.target/aarch64/simd/vqdmullh_lane_s16.c: Likewise.
	* gcc.target/aarch64/simd/vqdmullh_laneq_s16.c: Likewise.
	* gcc.target/aarch64/simd/vqdmulls_lane_s32.c: Likewise.
	* gcc.target/aarch64/simd/vqdmulls_laneq_s32.c: Likewise.
	* gcc.target/aarch64/sve/dup_lane_1.c: Likewise.
	* gcc.target/aarch64/sve/extract_1.c: Likewise.
	* gcc.target/aarch64/sve/extract_2.c: Likewise.
	* gcc.target/aarch64/sve/extract_3.c: Likewise.
	* gcc.target/aarch64/sve/extract_4.c: Likewise.
	* gcc.target/aarch64/sve/live_1.c: Update scan-assembler regex
	cases to look for 'b' and 'h' registers instead of 'w'.
	* gcc.target/arm/crypto-vsha1cq_u32.c: Update scan-assembler
	regex to reflect lane 0 vector extractions being simplified
	to scalar register moves.
	* gcc.target/arm/crypto-vsha1h_u32.c: Likewise.
	* gcc.target/arm/crypto-vsha1mq_u32.c: Likewise.
	* gcc.target/arm/crypto-vsha1pq_u32.c: Likewise.
	* gcc.target/arm/mve/intrinsics/vgetq_lane_f16.c: Extract
	lane 1 as the moves for lane 0 now get optimized away.
	* gcc.target/arm/mve/intrinsics/vgetq_lane_f32.c: Likewise.
	* gcc.target/arm/mve/intrinsics/vgetq_lane_s16.c: Likewise.
	* gcc.target/arm/mve/intrinsics/vgetq_lane_s32.c: Likewise.
	* gcc.target/arm/mve/intrinsics/vgetq_lane_s8.c: Likewise.
	* gcc.target/arm/mve/intrinsics/vgetq_lane_u16.c: Likewise.
	* gcc.target/arm/mve/intrinsics/vgetq_lane_u32.c: Likewise.
	* gcc.target/arm/mve/intrinsics/vgetq_lane_u8.c: Likewise.

2 files changed, 7 insertions, 6 deletions

diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index aef6da9..f12a0be 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -1884,15 +1884,16 @@
 )
 
 (define_insn "*zero_extend<SHORT:mode><GPI:mode>2_aarch64"
-  [(set (match_operand:GPI 0 "register_operand" "=r,r,w")
-        (zero_extend:GPI (match_operand:SHORT 1 "nonimmediate_operand" "r,m,m")))]
+  [(set (match_operand:GPI 0 "register_operand" "=r,r,w,r")
+        (zero_extend:GPI (match_operand:SHORT 1 "nonimmediate_operand" "r,m,m,w")))]
   ""
   "@
    and\t%<GPI:w>0, %<GPI:w>1, <SHORT:short_mask>
    ldr<SHORT:size>\t%w0, %1
-   ldr\t%<SHORT:size>0, %1"
-  [(set_attr "type" "logic_imm,load_4,f_loads")
-   (set_attr "arch" "*,*,fp")]
+   ldr\t%<SHORT:size>0, %1
+   umov\t%w0, %1.<SHORT:size>[0]"
+  [(set_attr "type" "logic_imm,load_4,f_loads,neon_to_gp")
+   (set_attr "arch" "*,*,fp,fp")]
 )
 
 (define_expand "<optab>qihi2"
diff --git a/gcc/config/arm/vfp.md b/gcc/config/arm/vfp.md
index 55b6c1a..93e96369 100644
--- a/gcc/config/arm/vfp.md
+++ b/gcc/config/arm/vfp.md
@@ -224,7 +224,7 @@
 ;; problems because small constants get converted into adds.
 (define_insn "*arm_movsi_vfp"
   [(set (match_operand:SI 0 "nonimmediate_operand" "=rk,r,r,r,rk,m ,*t,r,*t,*t, *Uv")
-      (match_operand:SI 1 "general_operand"	   "rk, I,K,j,mi,rk,r,*t,*t,*Uvi,*t"))]
+      (match_operand:SI 1 "general_operand"	   "rk, I,K,j,mi,rk,r,t,*t,*Uvi,*t"))]
   "TARGET_ARM && TARGET_HARD_FLOAT
    && (   s_register_operand (operands[0], SImode)
        || s_register_operand (operands[1], SImode))"