[FPEnv] Make constrained FP IR verification more flexible.

[kpn]

Summary

The IR verifier currently supports the constrained floating point intrinsics, but the implementation is hard to extend. It doesn't currently have an easy way to support intrinsics that, for example, lack a rounding mode. This will be needed for impending new constrained intrinsics.

This code is split out of D55897, which itself was split out of D43515.

[arsenm]

LGTM

[arsenm]

Actually, needs tests

[kpn]

No new observable behavior change is introduced by this patch. I believe the existing constrained intrinsic tests should exercise it pretty well. Is there a specific test that is needed?

[arsenm]

In D59830#1443346, @kpn wrote:

No new observable behavior change is introduced by this patch. I believe the existing constrained intrinsic tests should exercise it pretty well. Is there a specific test that is needed?

I grepped around and don't see these error messages in any verifier tests, so it seems like this isn't actually tested now

[arsenm]

In D59830#1443352, @arsenm wrote:

In D59830#1443346, @kpn wrote:

No new observable behavior change is introduced by this patch. I believe the existing constrained intrinsic tests should exercise it pretty well. Is there a specific test that is needed?

I grepped around and don't see these error messages in any verifier tests, so it seems like this isn't actually tested now

At least 2 of these cases are missing tests: https://llvm.org/reports/coverage/lib/IR/Verifier.cpp.gcov.html

[kpn]

Remove some unneeded, untested code and add a comment on why it is unneeded.

[arsenm]

LGTM

lib/IR/Verifier.cpp

static DISubprogram *getSubprogram(Metadata *LocalScope) {
 
   // Just return null; broken scope chains are checked elsewhere.
   assert(!isa<DILocalScope>(LocalScope) && "Unknown type of local scope");
   return nullptr;
 }
 
 void Verifier::visitConstrainedFPIntrinsic(ConstrainedFPIntrinsic &FPI) {
   unsigned NumOperands = FPI.getNumArgOperands();
-  Assert(((NumOperands == 5 && FPI.isTernaryOp()) ||
-          (NumOperands == 3 && FPI.isUnaryOp()) || (NumOperands == 4)),
-           "invalid arguments for constrained FP intrinsic", &FPI);
-  Assert(isa<MetadataAsValue>(FPI.getArgOperand(NumOperands-1)),
+  bool HasExceptionMD = false;
+  bool HasRoundingMD = false;
+  switch (FPI.getIntrinsicID()) {
+  case Intrinsic::experimental_constrained_sqrt:
+  case Intrinsic::experimental_constrained_sin:
+  case Intrinsic::experimental_constrained_cos:
+  case Intrinsic::experimental_constrained_exp:
+  case Intrinsic::experimental_constrained_exp2:
+  case Intrinsic::experimental_constrained_log:
+  case Intrinsic::experimental_constrained_log10:
+  case Intrinsic::experimental_constrained_log2:
+  case Intrinsic::experimental_constrained_rint:
+  case Intrinsic::experimental_constrained_nearbyint:
+  case Intrinsic::experimental_constrained_ceil:
+  case Intrinsic::experimental_constrained_floor:
+  case Intrinsic::experimental_constrained_round:
+  case Intrinsic::experimental_constrained_trunc:
+    Assert((NumOperands == 3), "invalid arguments for constrained FP intrinsic",
+           &FPI);
+    HasExceptionMD = true;
+    HasRoundingMD = true;
+    break;
+
+  case Intrinsic::experimental_constrained_fma:
+    Assert((NumOperands == 5), "invalid arguments for constrained FP intrinsic",
+           &FPI);
+    HasExceptionMD = true;
+    HasRoundingMD = true;
+    break;
+
+  case Intrinsic::experimental_constrained_fadd:
+  case Intrinsic::experimental_constrained_fsub:
+  case Intrinsic::experimental_constrained_fmul:
+  case Intrinsic::experimental_constrained_fdiv:
+  case Intrinsic::experimental_constrained_frem:
+  case Intrinsic::experimental_constrained_pow:
+  case Intrinsic::experimental_constrained_powi:
+  case Intrinsic::experimental_constrained_maxnum:
+  case Intrinsic::experimental_constrained_minnum:
+    Assert((NumOperands == 4), "invalid arguments for constrained FP intrinsic",
+           &FPI);
+    HasExceptionMD = true;
+    HasRoundingMD = true;
+    break;
+
+  default:
+    llvm_unreachable("Invalid constrained FP intrinsic!");
+  }
+
+  if (HasExceptionMD) {
+    Assert(isa<MetadataAsValue>(FPI.getArgOperand(NumOperands - 1)),
            "invalid exception behavior argument", &FPI);
-  Assert(isa<MetadataAsValue>(FPI.getArgOperand(NumOperands-2)),
+    Assert(FPI.getExceptionBehavior() != ConstrainedFPIntrinsic::ebInvalid,
+           "invalid exception behavior argument", &FPI);
+  }
+  if (HasRoundingMD) {
+    int RoundingIdx = (HasExceptionMD ? NumOperands - 2 : NumOperands - 1);
+    Assert(isa<MetadataAsValue>(FPI.getArgOperand(RoundingIdx)),
            "invalid rounding mode argument", &FPI);
     Assert(FPI.getRoundingMode() != ConstrainedFPIntrinsic::rmInvalid,
            "invalid rounding mode argument", &FPI);
-  Assert(FPI.getExceptionBehavior() != ConstrainedFPIntrinsic::ebInvalid,
-         "invalid exception behavior argument", &FPI);
+  }
 }
 
 void Verifier::visitDbgIntrinsic(StringRef Kind, DbgVariableIntrinsic &DII) {
   auto *MD = cast<MetadataAsValue>(DII.getArgOperand(0))->getMetadata();
   AssertDI(isa<ValueAsMetadata>(MD) ||
              (isa<MDNode>(MD) && !cast<MDNode>(MD)->getNumOperands()),
          "invalid llvm.dbg." + Kind + " intrinsic address/value", &DII, MD);
   AssertDI(isa<DILocalVariable>(DII.getRawVariable()),