[PATCH] D127584: [JITLink][AArch64] Implement MoveWide16 generic edge.

[Sunho Kim via Phabricator via llvm-commits]

sunho created this revision.
sunho added reviewers: lhames, sgraenitz.
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Implements MoveWide16 generic edge kind that can be used to patch MOVZ/MOVK (imm16) instructions.


https://reviews.llvm.org/D127584

Files:
  llvm/include/llvm/ExecutionEngine/JITLink/aarch64.h


Index: llvm/include/llvm/ExecutionEngine/JITLink/aarch64.h
===================================================================
--- llvm/include/llvm/ExecutionEngine/JITLink/aarch64.h
+++ llvm/include/llvm/ExecutionEngine/JITLink/aarch64.h
@@ -28,6 +28,7 @@
   Pointer64Anon,
   Page21,
   PageOffset12,
+  MoveWide16,
   GOTPage21,
   GOTPageOffset12,
   TLVPage21,
@@ -72,6 +73,25 @@
   return 0;
 }
 
+// Returns whether the Instr is MOVK/MOVZ (imm16) with a zero immediate field
+inline bool isMoveWideImm16(uint32_t Instr) {
+  constexpr uint32_t MoveWideImm16Mask = 0x5f9fffe0;
+  return (Instr & MoveWideImm16Mask) == 0x52800000;
+}
+
+// Returns the amount the address operand of MOVK/MOVZ (imm16)
+// should be shifted right by.
+//
+// The shift value is specfied in the assembly as LSL #<shift>.
+inline unsigned getMoveWide16Shift(uint32_t Instr) {
+  if (isMoveWideImm16(Instr)) {
+    uint32_t ImplicitShift = (Instr >> 21) & 0b11;
+    return ImplicitShift << 4;
+  }
+
+  return 0;
+}
+
 /// Apply fixup expression for edge to block content.
 inline Error applyFixup(LinkGraph &G, Block &B, const Edge &E) {
   using namespace support;
@@ -152,6 +172,20 @@
     *(ulittle32_t *)FixupPtr = FixedInstr;
     break;
   }
+  case MoveWide16: {
+    uint64_t TargetOffset =
+        (E.getTarget().getAddress() + E.getAddend()).getValue();
+
+    uint32_t RawInstr = *(ulittle32_t *)FixupPtr;
+    assert(isMoveWideImm16(RawInstr) &&
+           "RawInstr isn't a MOVK/MOVZ instruction");
+
+    unsigned ImmShift = getMoveWide16Shift(RawInstr);
+    uint32_t Imm = (TargetOffset >> ImmShift) & 0xffff;
+    uint32_t FixedInstr = RawInstr | (Imm << 5);
+    *(ulittle32_t *)FixupPtr = FixedInstr;
+    break;
+  }
   case LDRLiteral19: {
     assert((FixupAddress.getValue() & 0x3) == 0 && "LDR is not 32-bit aligned");
     assert(E.getAddend() == 0 && "LDRLiteral19 with non-zero addend");


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