[PATCH] D15320: CodeGen: Redo analyzePhysRegs() and computeRegisterLiveness()

[JF Bastien via llvm-commits]

jfb added inline comments.

================
Comment at: lib/Target/X86/X86InstrInfo.cpp:4446
@@ +4445,3 @@
+    if (!AXDead) {
+      // FIXME: If computeRegisterLiveness() reported LQR_Unknown and AX is
+      // dead even though we couldn't determine that, then we are reading an
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hfinkel wrote:
> This seems like an odd FIXME to keep now that we have a way to detect the situation. Why don't you detect the LQR_Unknown here and abort instead of doing something the verifier will complain about? Then we can have a FIXME that we really should be using some real analysis here instead of a local search.
I'm not sure I understand what you're suggesting, maybe the new FIXME isn't clear enough: you're right that a real analysis would fix the issue, but if the current one says unknown then we have to save/restore AX otherwise we may be clobbering live state. It's better to complain at verification time rather than to clobber state!


Repository:
  rL LLVM

http://reviews.llvm.org/D15320