[PATCH] D24228: [Thumb] Save/restore high registers in Thumb1 pro/epilogues

[Tim Northover via llvm-commits]

t.p.northover added inline comments.

================
Comment at: lib/Target/ARM/Thumb1FrameLowering.cpp:641-643
@@ +640,5 @@
+    } else {
+      // FIXME: This gets hit when using SjLj exceptions, as
+      // ARM::Int_eh_sjlj_dispatchsetup clobbers the FP registers.
+      //llvm_unreachable("callee-saved register of unexpected class");
+    }
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Stale comment? Certainly a scary one.

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Comment at: lib/Target/ARM/Thumb1FrameLowering.cpp:688-690
@@ +687,5 @@
+  // Find the first register to save.
+  auto HiRegToSave = AllHighRegs.begin();
+  while (HiRegToSave != AllHighRegs.end() && !HiRegsToSave.count(*HiRegToSave))
+    ++HiRegToSave;
+
----------------
This 3-line fragment seems to be an extremely common idiom in this stretch of code. Might be worth factoring into a `findNextOrderedReg`, or even using sorted vectors of registers to sidestep the issue entirely.


https://reviews.llvm.org/D24228