[PATCH] D97968: [AArch64][GlobalISel][RegBankSelect] Improve rbs of G_BUILD_VECTOR when fed by fp values.

[Amara Emerson via Phabricator via llvm-commits]

aemerson created this revision.
aemerson added a reviewer: paquette.
aemerson added a project: LLVM.
Herald added subscribers: danielkiss, hiraditya, kristof.beyls, rovka.
aemerson requested review of this revision.

This is actually two changes. One is to avoid copies when fp values are fed into a build_vector, without being able to tell from the opcode.

The other is that build_vectors are also marked as only defining FP, since they produce vector results.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D97968

Files:
  llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/regbankselect-build-vector.mir


Index: llvm/test/CodeGen/AArch64/GlobalISel/regbankselect-build-vector.mir
===================================================================
--- llvm/test/CodeGen/AArch64/GlobalISel/regbankselect-build-vector.mir
+++ llvm/test/CodeGen/AArch64/GlobalISel/regbankselect-build-vector.mir
@@ -69,3 +69,43 @@
     RET_ReallyLR implicit $q0
 
 ...
+---
+name:            fed_by_fp_load
+alignment:       4
+legalized:       true
+tracksRegLiveness: true
+liveins:
+  - { reg: '$x0' }
+  - { reg: '$x1' }
+  - { reg: '$x2' }
+  - { reg: '$s0' }
+frameInfo:
+  maxAlignment:    1
+body:             |
+  bb.1:
+    liveins: $s0, $x0, $x1, $x2
+
+    ; CHECK-LABEL: name: fed_by_fp_load
+    ; CHECK: liveins: $s0, $x0, $x1, $x2
+    ; CHECK: [[COPY:%[0-9]+]]:gpr(p0) = COPY $x0
+    ; CHECK: [[C:%[0-9]+]]:gpr(s64) = G_CONSTANT i64 328
+    ; CHECK: [[PTR_ADD:%[0-9]+]]:gpr(p0) = G_PTR_ADD [[COPY]], [[C]](s64)
+    ; CHECK: [[C1:%[0-9]+]]:gpr(s64) = G_CONSTANT i64 344
+    ; CHECK: [[PTR_ADD1:%[0-9]+]]:gpr(p0) = G_PTR_ADD [[COPY]], [[C1]](s64)
+    ; CHECK: [[LOAD:%[0-9]+]]:fpr(s32) = G_LOAD [[PTR_ADD]](p0) :: (load 4)
+    ; CHECK: [[LOAD1:%[0-9]+]]:fpr(s32) = G_LOAD [[PTR_ADD1]](p0) :: (load 4)
+    ; CHECK: [[BUILD_VECTOR:%[0-9]+]]:fpr(<2 x s32>) = G_BUILD_VECTOR [[LOAD]](s32), [[LOAD1]](s32)
+    ; CHECK: $d0 = COPY [[BUILD_VECTOR]](<2 x s32>)
+    ; CHECK: RET_ReallyLR implicit $d0
+    %0:_(p0) = COPY $x0
+    %4:_(s64) = G_CONSTANT i64 328
+    %5:_(p0) = G_PTR_ADD %0, %4(s64)
+    %6:_(s64) = G_CONSTANT i64 344
+    %7:_(p0) = G_PTR_ADD %0, %6(s64)
+    %15:_(s32) = G_LOAD %5(p0) :: (load 4)
+    %20:_(s32) = G_LOAD %7(p0) :: (load 4)
+    %21:_(<2 x s32>) = G_BUILD_VECTOR %15(s32), %20(s32)
+    $d0 = COPY %21(<2 x s32>)
+    RET_ReallyLR implicit $d0
+
+...
Index: llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp
===================================================================
--- llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp
+++ llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp
@@ -527,6 +527,8 @@
   case TargetOpcode::G_UITOFP:
   case TargetOpcode::G_EXTRACT_VECTOR_ELT:
   case TargetOpcode::G_INSERT_VECTOR_ELT:
+  case TargetOpcode::G_BUILD_VECTOR:
+  case TargetOpcode::G_BUILD_VECTOR_TRUNC:
     return true;
   default:
     break;
@@ -880,7 +882,8 @@
         }))
       break;
     if (isPreISelGenericFloatingPointOpcode(DefOpc) ||
-        SrcTy.getSizeInBits() < 32) {
+        SrcTy.getSizeInBits() < 32 ||
+        getRegBank(VReg, MRI, TRI) == &AArch64::FPRRegBank) {
       // Have a floating point op.
       // Make sure every operand gets mapped to a FPR register class.
       unsigned NumOperands = MI.getNumOperands();


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