[PATCH] D19046: Introduce a "patchable-prologue" function attribute

[Reid Kleckner via llvm-commits]

rnk added inline comments.

================
Comment at: include/llvm/Target/TargetLowering.h:1805
@@ +1804,3 @@
+  virtual void
+  makeFunctionProloguePatchable(MachineFunction &MF,
+                                PatchablePrologueFlavor PPF) const {
----------------
This is about the prologue, so I would put this in TargetFrameLowering / X86FrameLowering, rather than growing the massive TargetLowering interface.

================
Comment at: include/llvm/Target/TargetLowering.h:1807
@@ +1806,3 @@
+                                PatchablePrologueFlavor PPF) const {
+    llvm_unreachable("Not implemented for this target!");
+  }
----------------
This file is not consistent on this point, but this should be report_fatal_error, since we want to keep the message in release builds.

================
Comment at: lib/Target/X86/X86ISelLowering.cpp:30642
@@ +30641,3 @@
+  case X86::SUB64ri32:
+    // We know this instruction takes more than two bytes.
+    break;
----------------
I guess we are confident that modifying an instruction during its execution is not problematic.


http://reviews.llvm.org/D19046