[InstCombine] Do not introduce bitcasts for swifterror arguments.

[fhahn]

Summary

The following constraints hold for swifterror values:

A swifterror value (either the parameter or the alloca) can only
be loaded and stored from, or used as a swifterror argument.

This patch updates instcombine to not try to convert a bitcast of a
function into a bitcast of a swifterror argument.

[lebedev.ri]

FWIW this patch is consistent with what i have seen; although i'm not faimiliar with that function so i can't say whether or not that is the right fix.

[vsk]

llvm/test/Transforms/InstCombine/swifterror-argument-bitcast-fold.ll

3

Just a drive-by question/comment -- is a check line needed here? I assumed FileCheck complains if it doesn't find one.

[fhahn]

llvm/test/Transforms/InstCombine/swifterror-argument-bitcast-fold.ll

3

arg, it should have added check lines.......... Will update

[rjmccall]

LGTM. Untyped pointers can't come soon enough.

[fhahn]

Add proper RUN & CHECK lines to test.

[vsk]

Test changes look reasonable to me!

[fhahn]

Thanks for taking a look! Anyone willing to mark as approved in Phabricator?

[fhahn]

Thanks everyone!

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
 
     if (AttrBuilder(CallerPAL.getParamAttributes(i))
             .overlaps(AttributeFuncs::typeIncompatible(ParamTy)))
       return false;   // Attribute not compatible with transformed value.
 
     if (Call.isInAllocaArgument(i))
       return false;   // Cannot transform to and from inalloca.
 
+    if (CallerPAL.hasParamAttribute(i, Attribute::SwiftError))
+      return false;
+
     // If the parameter is passed as a byval argument, then we have to have a
     // sized type and the sized type has to have the same size as the old type.
     if (ParamTy != ActTy && CallerPAL.hasParamAttribute(i, Attribute::ByVal)) {
       PointerType *ParamPTy = dyn_cast<PointerType>(ParamTy);
       if (!ParamPTy || !ParamPTy->getElementType()->isSized())
         return false;
 
       Type *CurElTy = Call.getParamByValType(i);

llvm/test/Transforms/InstCombine/swifterror-argument-bitcast-fold.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -instcombine -S %s | FileCheck %s
+
+; The swifterror value can only be loaded, stored or used as swifterror
+; argument. Make sure we do not try to turn the function bitcast into an
+; argument bitcast.
+define swiftcc void @spam(i32** swifterror %arg) {
+; CHECK-LABEL: @spam(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    call swiftcc void bitcast (void (i64**)* @widget to void (i32**)*)(i32** swifterror [[ARG:%.*]])
+; CHECK-NEXT:    ret void
+;
+bb:
+  call swiftcc void bitcast (void (i64**)* @widget to void (i32**)*)(i32** swifterror %arg)
+  ret void
+}
+
+declare swiftcc void @widget(i64**)