[msan] Generalize handleIntrinsicByApplyingToShadow by adding bitcasting (#123474)

`handleIntrinsicByApplyingToShadow` (introduced in
#114490) requires that the
intrinsic supports integer-ish operands; this is not the case for all
intrinsics. This patch generalizes the function to bitcast the shadow
arguments to be the same type as the original intrinsic, thus
guaranteeing that the intrinsic exists. Additionally, it casts the
computed shadow to be an appropriate shadow type.

This function assumes that the intrinsic will handle arbitrary
bit-patterns (for example, if the intrinsic accepts floats for var1, we
assume that it works normally even if inputs are NaNs etc.).

Author: thurstond

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

@@ -4008,6 +4008,10 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
   ///     shadow[out] =
   ///         intrinsic(shadow[var1], shadow[var2], opType) | shadow[opType]
   ///
+  /// CAUTION: this assumes that the intrinsic will handle arbitrary
+  ///          bit-patterns (for example, if the intrinsic accepts floats for
+  ///          var1, we require that it doesn't care if inputs are NaNs).
+  ///
   /// For example, this can be applied to the Arm NEON vector table intrinsics
   /// (tbl{1,2,3,4}).
   ///
@@ -4022,7 +4026,11 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     // Don't use getNumOperands() because it includes the callee
     for (unsigned int i = 0; i < I.arg_size() - trailingVerbatimArgs; i++) {
       Value *Shadow = getShadow(&I, i);
-      ShadowArgs.push_back(Shadow);
+
+      // Shadows are integer-ish types but some intrinsics require a
+      // different (e.g., floating-point) type.
+      ShadowArgs.push_back(
+          IRB.CreateBitCast(Shadow, I.getArgOperand(i)->getType()));
     }
 
     for (unsigned int i = I.arg_size() - trailingVerbatimArgs; i < I.arg_size();
@@ -4043,7 +4051,7 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
       CombinedShadow = IRB.CreateOr(Shadow, CombinedShadow, "_msprop");
     }
 
-    setShadow(&I, CombinedShadow);
+    setShadow(&I, IRB.CreateBitCast(CombinedShadow, getShadowTy(&I)));
 
     setOriginForNaryOp(I);
   }