[llvm] [Clang][inlineasm] Add special support for "rm" output constraints (PR #92040)

[Matt Arsenault via llvm-commits]

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@@ -496,6 +496,8 @@ class TargetPassConfig : public ImmutablePass {
 void registerCodeGenCallback(PassInstrumentationCallbacks &PIC,
                              LLVMTargetMachine &);
 
+bool usesGreedyOrDefaultRegisterAllocator();
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arsenm wrote:

This doesn't work in general and "default" allocator is ambiguous. I'm -1 on anything that tries to expose the allocator in use to clang. I thought the result of the issue thread was fast RA would just start spilling everything? 

https://github.com/llvm/llvm-project/pull/92040