Commit Graph

2 Commits

Author SHA1 Message Date
Alex Richardson b5f69e234e Handle BUNDLE instructions in MipsAsmPrinter
Summary:
In our CHERI fork we use BUNDLE instructions to ensure that a
three-instruction sequence to generate a program-counter-relative value is
emitted without reordering or insertions (since that would break the 32-bit
offset computation).

Currently MipsAsmPrinter asserts when it encounters a pseudo instruction.
To handle BUNDLE we can simply skip the instruction which will then make
EmitInstruction() process the contents of the bundle in order.

Reviewers: atanasyan

Reviewed By: atanasyan

Subscribers: merge_guards_bot, sdardis, hiraditya, jrtc27, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70945
2019-12-04 11:30:00 +00:00
Alex Richardson b91f239485 MipsDelaySlotFiller: Don't move BUNDLE instructions into the delay slot
Summary:
In our CHERI fork we use BUNDLE instructions to ensure that a
three-instruction sequence to generate a program-counter-relative value is
emitted without reordering or insertions (since that would break the 32-bit
offset computation). This sequence is created in MipsExpandPseudo and we use
finalizeBundle() to create the BUNDLE instruction.

However, the delay slot filler currently breaks this pattern since the BUNDLE
will be removed and so all instructions are moved into the delay slot.
Since the delay slot only executes the first instruction, this results in
incorrect computations (and run-time crashes) if the branch is taken.

The original test cases uses CHERI instructions, so for the test case here
I simple filled a BUNDLE with a no-op DADDiu $sp_64, -16 and DADDiu $sp_64, 16.

Reviewers: atanasyan

Reviewed By: atanasyan

Subscribers: merge_guards_bot, sdardis, hiraditya, jrtc27, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70944
2019-12-04 11:30:00 +00:00