[llvm] [ARM] Add early-clobber to MVE VCMLA.f32 (PR #114995)

[Oliver Stannard via llvm-commits]

https://github.com/ostannard created https://github.com/llvm/llvm-project/pull/114995

This instruction (but not the f16 variant) cannot us the same register for the output as either of the inputs, so it needs to be marked as early-clobber.

>From 8cae06442356a631eb0bc576279b4a7b6eb45e69 Mon Sep 17 00:00:00 2001
From: Oliver Stannard <oliver.stannard at arm.com>
Date: Mon, 4 Nov 2024 11:17:48 +0000
Subject: [PATCH] [ARM] Add early-clobber to MVE VCMLA.f32

This instruction (but not the f16 variant) cannot us the same register
for the output as either of the inputs, so it needs to be marked as
early-clobber.
---
 llvm/lib/Target/ARM/ARMInstrMVE.td    | 10 +++++-----
 llvm/test/CodeGen/Thumb2/mve-vcmla.ll | 24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/Target/ARM/ARMInstrMVE.td b/llvm/lib/Target/ARM/ARMInstrMVE.td
index 8c8403ac58b080..22af599f4f0859 100644
--- a/llvm/lib/Target/ARM/ARMInstrMVE.td
+++ b/llvm/lib/Target/ARM/ARMInstrMVE.td
@@ -3583,10 +3583,10 @@ def ARMimmOneH: PatLeaf<(bitconvert (v8i16 (ARMvmovImm (i32 2620))))>; // 1.0 ha
 defm MVE_VMULf32 : MVE_VMUL_fp_m<MVE_v4f32, ARMimmOneF>;
 defm MVE_VMULf16 : MVE_VMUL_fp_m<MVE_v8f16, ARMimmOneH>;
 
-class MVE_VCMLA<string suffix, bits<2> size>
+class MVE_VCMLA<string suffix, bits<2> size, string cstr>
   : MVEFloatArithNeon<"vcmla", suffix, size{1}, (outs MQPR:$Qd),
                          (ins MQPR:$Qd_src, MQPR:$Qn, MQPR:$Qm, complexrotateop:$rot),
-                         "$Qd, $Qn, $Qm, $rot", vpred_n, "$Qd = $Qd_src", size, []> {
+                         "$Qd, $Qn, $Qm, $rot", vpred_n, "$Qd = $Qd_src"#cstr, size, []> {
   bits<4> Qd;
   bits<4> Qn;
   bits<2> rot;
@@ -3603,8 +3603,8 @@ class MVE_VCMLA<string suffix, bits<2> size>
   let Inst{4} = 0b0;
 }
 
-multiclass MVE_VCMLA_m<MVEVectorVTInfo VTI> {
-  def "" : MVE_VCMLA<VTI.Suffix, VTI.Size>;
+multiclass MVE_VCMLA_m<MVEVectorVTInfo VTI, string cstr=""> {
+  def "" : MVE_VCMLA<VTI.Suffix, VTI.Size, cstr>;
   defvar Inst = !cast<Instruction>(NAME);
 
   let Predicates = [HasMVEFloat] in {
@@ -3633,7 +3633,7 @@ multiclass MVE_VCMLA_m<MVEVectorVTInfo VTI> {
 }
 
 defm MVE_VCMLAf16 : MVE_VCMLA_m<MVE_v8f16>;
-defm MVE_VCMLAf32 : MVE_VCMLA_m<MVE_v4f32>;
+defm MVE_VCMLAf32 : MVE_VCMLA_m<MVE_v4f32, ", at earlyclobber $Qd">;
 
 class MVE_VADDSUBFMA_fp<string iname, string suffix, bits<2> size, bit bit_4,
                         bit bit_8, bit bit_21, dag iops=(ins),
diff --git a/llvm/test/CodeGen/Thumb2/mve-vcmla.ll b/llvm/test/CodeGen/Thumb2/mve-vcmla.ll
index d1976472e39460..df542be73c58cb 100644
--- a/llvm/test/CodeGen/Thumb2/mve-vcmla.ll
+++ b/llvm/test/CodeGen/Thumb2/mve-vcmla.ll
@@ -121,3 +121,27 @@ entry:
   %res = fadd <4 x float> %d, %a
   ret <4 x float> %res
 }
+
+define arm_aapcs_vfpcc <8 x half> @same_register_f16(<8 x half> %a) {
+; CHECK-LABEL: same_register_f16:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    vcmla.f16 q0, q0, q0, #0
+; CHECK-NEXT:    bx lr
+entry:
+  %d = tail call <8 x half> @llvm.arm.mve.vcmlaq.v8f16(i32 0, <8 x half> zeroinitializer, <8 x half> %a, <8 x half> %a)
+  %res = fadd fast <8 x half> %d, %a
+  ret <8 x half> %res
+}
+
+define arm_aapcs_vfpcc <4 x float> @same_register_f32(<4 x float> %a) {
+; CHECK-LABEL: same_register_f32:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    vmov q1, q0
+; CHECK-NEXT:    vcmla.f32 q1, q0, q0, #0
+; CHECK-NEXT:    vmov q0, q1
+; CHECK-NEXT:    bx lr
+entry:
+  %d = tail call <4 x float> @llvm.arm.mve.vcmlaq.v4f32(i32 0, <4 x float> zeroinitializer, <4 x float> %a, <4 x float> %a)
+  %res = fadd fast <4 x float> %d, %a
+  ret <4 x float> %res
+}