[clang] [llvm] [mlir] [AMDGPU] Add the support for 45-bit buffer resource (PR #159702)

[Krzysztof Drewniak via llvm-commits]

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@@ -5905,33 +5905,42 @@ bool AMDGPULegalizerInfo::legalizePointerAsRsrcIntrin(
   Register Flags = MI.getOperand(5).getReg();
 
   LLT S32 = LLT::scalar(32);
+  LLT S64 = LLT::scalar(64);
 
   B.setInsertPt(B.getMBB(), ++B.getInsertPt());
-  auto Unmerge = B.buildUnmerge(S32, Pointer);
-  Register LowHalf = Unmerge.getReg(0);
-  Register HighHalf = Unmerge.getReg(1);
-
-  auto AndMask = B.buildConstant(S32, 0x0000ffff);
-  auto Masked = B.buildAnd(S32, HighHalf, AndMask);
-
-  MachineInstrBuilder NewHighHalf = Masked;
-  std::optional<ValueAndVReg> StrideConst =
-      getIConstantVRegValWithLookThrough(Stride, MRI);
-  if (!StrideConst || !StrideConst->Value.isZero()) {
-    MachineInstrBuilder ShiftedStride;
-    if (StrideConst) {
-      uint32_t StrideVal = StrideConst->Value.getZExtValue();
-      uint32_t ShiftedStrideVal = StrideVal << 16;
-      ShiftedStride = B.buildConstant(S32, ShiftedStrideVal);
-    } else {
-      auto ExtStride = B.buildAnyExt(S32, Stride);
-      auto ShiftConst = B.buildConstant(S32, 16);
-      ShiftedStride = B.buildShl(S32, ExtStride, ShiftConst);
-    }
-    NewHighHalf = B.buildOr(S32, Masked, ShiftedStride);
+
+  if (ST.has45BitNumRecordsBufferResource()) {
+    // Build the lower 64-bit value, which has a 57-bit base and the lower 7-bit
+    // num_records.
+    LLT PtrIntTy = LLT::scalar(MRI.getType(Pointer).getSizeInBits());
+    auto PointerInt = B.buildPtrToInt(PtrIntTy, Pointer);
+    auto ExtPointer = B.buildAnyExtOrTrunc(S64, PointerInt);
+    auto NumRecordsLHS = B.buildShl(S64, NumRecords, B.buildConstant(S32, 57));
+    Register LowHalf = B.buildOr(S64, ExtPointer, NumRecordsLHS).getReg(0);
+
+    // Build the higher 64-bit value, which has the higher 38-bit num_records,
+    // 6-bit zero (omit), 14-bit stride and 6-bit zero (omit).
+    auto NumRecordsRHS = B.buildLShr(S64, NumRecords, B.buildConstant(S32, 7));
+    auto ExtStride = B.buildAnyExt(S64, Stride);
+    auto ShiftedStride = B.buildShl(S64, ExtStride, B.buildConstant(S32, 44));
+    Register HighHalf = B.buildOr(S64, NumRecordsRHS, ShiftedStride).getReg(0);
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krzysz00 wrote:

Same note re flags

https://github.com/llvm/llvm-project/pull/159702