The 'fake use' asm gadget does not always keep variables alive. E.g., in
rdar://57754659, llvm was unable to preserve two local variables despite
the use of these gadgets. These variables were backed by a LoadInst and
an ExtractValueInst respectively. Instead of emitting shadow copies for
just those kinds of instructions, use shadow copies exclusively. This
may cause more variables to appear in the debugger window before they
are initialized, but should result in fewer variables being dropped.
rdar://57754659
This option is useful to debug the compiler itself, to simulate debug info as it
would be generated when producing optimized code, but without the unpredictable
output of an optimizing debugger.
And include some supplementary mangling changes:
- Give the first generic param (depth=0, index=0) a single character mangling. Even after removing the self type from method declaration types, 'Self' still shows up very frequently in protocol requirement signatures.
- Fix the mangling of generic parameter counts to elide the count when there's only one parameter at the starting depth of the mangling.
Together these carve another 154KB out of a debug standard library. There's some awkwardness in demangled strings that I'll clean up in subsequent commits; since decl types now only mangle the number of generic params at their own depth, it's context-dependent what depths those represent, which we get wrong now. Currying markers are also wrong, but since free function currying is going away, we can mangle the partial application thunks in different ways.
Swift SVN r32896
'Ss' appears in manglings tens of thousands of times in the standard library and is also incredibly frequent in other modules. This alone is enough to shrink the standard library by 59KB.
Swift SVN r32409
Most tests were using %swift or similar substitutions, which did not
include the target triple and SDK. The driver was defaulting to the
host OS. Thus, we could not run the tests when the standard library was
not built for OS X.
Swift SVN r24504
