[llvm] [AMDGPU] support 64-bit immediates in SIInstrInfo::FoldImmediate (PR #69260)

[Jay Foad via llvm-commits]

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@@ -3220,19 +3219,45 @@ bool SIInstrInfo::FoldImmediate(MachineInstr &UseMI, MachineInstr &DefMI,
   if (!ImmOp->isImm())
     return false;
 
+  auto getImmFor = [ImmOp](const MachineOperand &UseOp) -> int64_t {
+    int64_t Imm = ImmOp->getImm();
+    switch (UseOp.getSubReg()) {
+    default:
+      return Imm;
+    case AMDGPU::sub0:
+      return Lo_32(Imm);
+    case AMDGPU::sub1:
+      return Hi_32(Imm);
+    case AMDGPU::lo16:
+      return APInt(16, Imm).getSExtValue();
+    case AMDGPU::hi16:
+      return APInt(32, Imm).ashr(16).getSExtValue();
+    case AMDGPU::sub1_lo16:
+      return APInt(16, Hi_32(Imm)).getSExtValue();
+    case AMDGPU::sub1_hi16:
+      return APInt(32, Hi_32(Imm)).ashr(16).getSExtValue();
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jayfoad wrote:

int16_t is signed so the implicit conversion to the return type will sign extend it.

https://github.com/llvm/llvm-project/pull/69260