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

[Pierre van Houtryve 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: {
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Pierre-vh wrote:

I think lengthy `case` statements with a nested switch should go into a separate helper function.
It would be more readable IMO.

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