[PATCH] D122559: [AArch64][GlobalISel] Add new MOVI pattern for fp constants

[Allen zhong via Phabricator via llvm-commits]

Allen created this revision.
Allen added reviewers: dmgreen, fhahn, efriedma, sdesmalen, david-arm, paulwalker-arm.
Herald added subscribers: hiraditya, kristof.beyls, rovka.
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Allen requested review of this revision.
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GlobalISel is used in option -O0, so add MOVI pattern for it,
which is done similar in gcc.(https://godbolt.org/z/8j6fzG3h6)

      

Fix https://github.com/llvm/llvm-project/issues/53651


https://reviews.llvm.org/D122559

Files:
  llvm/lib/Target/AArch64/AArch64InstrFormats.td
  llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
  llvm/test/CodeGen/AArch64/fast-isel-const-float.ll


Index: llvm/test/CodeGen/AArch64/fast-isel-const-float.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/fast-isel-const-float.ll
@@ -0,0 +1,14 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=aarch64-none-linux-gnu -global-isel -verify-machineinstrs < %s | FileCheck %s --check-prefix=GISEL
+
+; float foo(void) { return float(2147483648); }
+define float @select_fp_const() {
+; CHECK-LABEL: select_opt4
+; CHECK: movi v0.2s, #79, lsl #24
+; GISEL-LABEL: select_fp_const:
+; GISEL:       // %bb.0: // %entry
+; GISEL-NEXT:    movi v0.2s, #79, lsl #24
+; GISEL-NEXT:    ret
+entry:
+  ret float 0x41E0000000000000
+}
Index: llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
===================================================================
--- llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
+++ llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
@@ -437,6 +437,9 @@
                      int OpIdx = -1) const;
   void renderFPImm64(MachineInstrBuilder &MIB, const MachineInstr &MI,
                      int OpIdx = -1) const;
+  void renderFPImm32SIMDModImmType4(MachineInstrBuilder &MIB,
+                                    const MachineInstr &MI,
+                                    int OpIdx = -1) const;
 
   // Materialize a GlobalValue or BlockAddress using a movz+movk sequence.
   void materializeLargeCMVal(MachineInstr &I, const Value *V, unsigned OpFlags);
@@ -6854,6 +6857,17 @@
       AArch64_AM::getFP64Imm(MI.getOperand(1).getFPImm()->getValueAPF()));
 }
 
+void AArch64InstructionSelector::renderFPImm32SIMDModImmType4(
+    MachineInstrBuilder &MIB, const MachineInstr &MI, int OpIdx) const {
+  assert(MI.getOpcode() == TargetOpcode::G_FCONSTANT && OpIdx == -1 &&
+         "Expected G_FCONSTANT");
+  MIB.addImm(AArch64_AM::encodeAdvSIMDModImmType4(MI.getOperand(1)
+                                                      .getFPImm()
+                                                      ->getValueAPF()
+                                                      .bitcastToAPInt()
+                                                      .getZExtValue()));
+}
+
 bool AArch64InstructionSelector::isLoadStoreOfNumBytes(
     const MachineInstr &MI, unsigned NumBytes) const {
   if (!MI.mayLoadOrStore())
Index: llvm/lib/Target/AArch64/AArch64InstrFormats.td
===================================================================
--- llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -1248,6 +1248,9 @@
   GISDNodeXFormEquiv<fpimm32XForm>;
 def gi_fpimm64 : GICustomOperandRenderer<"renderFPImm64">,
   GISDNodeXFormEquiv<fpimm64XForm>;
+def gi_fpimm32SIMDModImmType4 :
+    GICustomOperandRenderer<"renderFPImm32SIMDModImmType4">,
+  GISDNodeXFormEquiv<fpimm32SIMDModImmType4XForm>;
 
 // Vector lane operands
 class AsmVectorIndex<int Min, int Max, string NamePrefix=""> : AsmOperandClass {


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