[llvm] [llvm][ARM] Add a cortex-m4f alignment hazard recognizer (PR #126991)

[Jon Roelofs via llvm-commits]

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@@ -5455,6 +5473,21 @@ bool ARMBaseInstrInfo::hasNOP() const {
   return Subtarget.hasFeature(ARM::HasV6KOps);
 }
 
+void ARMBaseInstrInfo::insertNoop(MachineBasicBlock &MBB,
+                                  MachineBasicBlock::iterator MI) const {
+  DebugLoc DL;
+  if (hasNOP()) {
+    BuildMI(MBB, MI, DL, get(ARM::HINT)).addImm(0).addImm(ARMCC::AL).addImm(0);
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jroelofs wrote:

Oops, that should be `tHINT`. `hasNOP()` is the architectural check you're thinking of though.

https://developer.arm.com/documentation/ddi0419/c/Application-Level-Architecture/Thumb-Instruction-Details/Alphabetical-list-of-ARMv6-M-Thumb-instructions/NOP?lang=en

Funny that it still worked out and emitted the 16-bit version despite that typo.

https://github.com/llvm/llvm-project/pull/126991