[llvm] [AMDGPU] MCExpr printing helper with KnownBits support (PR #95951)

[Matt Arsenault via llvm-commits]

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@@ -303,3 +305,360 @@ const AMDGPUMCExpr *AMDGPUMCExpr::createOccupancy(unsigned InitOcc,
                  CreateExpr(InitOcc), NumSGPRs, NumVGPRs},
                 Ctx);
 }
+
+static KnownBits fromOptionalToKnownBits(std::optional<bool> CompareResult) {
+  const unsigned BitWidth = 64;
+  const APInt True(BitWidth, 1, /*isSigned=*/false);
+  const APInt False(BitWidth, 0, /*isSigned=*/false);
+  if (CompareResult) {
+    return *CompareResult ? KnownBits::makeConstant(True)
+                          : KnownBits::makeConstant(False);
+  }
+
+  KnownBits UnknownBool(/*BitWidth=*/1);
+  return UnknownBool.zext(BitWidth);
+}
+
+using KnownBitsMap = std::unordered_map<const MCExpr *, KnownBits>;
+
+void KnownBitsMapHelper(const MCExpr *Expr, KnownBitsMap &KBM, unsigned depth) {
+  const unsigned BitWidth = 64;
+  const APInt False(BitWidth, 0, /*isSigned=*/false);
+
+  int64_t Val;
+  if (Expr->evaluateAsAbsolute(Val)) {
+    APInt APValue(BitWidth, Val, /*isSigned=*/true);
+    KBM[Expr] = KnownBits::makeConstant(APValue);
+    return;
+  }
+
+  if (depth == 0) {
+    KBM[Expr] = KnownBits(BitWidth);
+    return;
+  }
+
+  depth--;
+
+  switch (Expr->getKind()) {
+  case MCExpr::ExprKind::Binary: {
+    const MCBinaryExpr *BExpr = cast<MCBinaryExpr>(Expr);
+    const MCExpr *LHS = BExpr->getLHS();
+    const MCExpr *RHS = BExpr->getRHS();
+
+    KnownBitsMapHelper(LHS, KBM, depth);
+    KnownBitsMapHelper(RHS, KBM, depth);
+    KnownBits LHSKnown = KBM[LHS];
+    KnownBits RHSKnown = KBM[RHS];
+    std::optional<bool> CompareRes;
+
+    switch (BExpr->getOpcode()) {
+    default:
+      KBM[Expr] = KnownBits(BitWidth);
+      return;
+    case MCBinaryExpr::Opcode::Add:
+      KBM[Expr] =
+          KnownBits::computeForAddSub(/*Add=*/true, /*NSW=*/false,
+                                      /*NUW=*/false, LHSKnown, RHSKnown);
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arsenm wrote:

There's a new add/sub helper 

https://github.com/llvm/llvm-project/pull/95951