tree 4142b4ad82afbec967c6b1d0b35acad3b728d1df
parent cacb637670e59c15cd4ad4668b21cadfc6318ab0
author Dylan McKay <me@dylanmckay.io> 1547955668 +0000
committer Dylan McKay <me@dylanmckay.io> 1547955668 +0000

[AVR] Fix codegen bug in 16-bit loads

Prior to this patch, the AVR::LDWRdPtr instruction was always lowered to
instructions of this pattern:

    ld  $GPR8, [PTR:XYZ]+
    ld  $GPR8, [PTR]+1

This has a problem; the [PTR] is incremented in-place once, but never
decremented.

Future uses of the same pointer will use the now clobbered value,
leading to the pointer being incorrect by an offset of one.

This patch modifies the expansion code of the LDWRdPtr pseudo
instruction so that the pointer variable is not silently clobbered in
future uses in the same live range.

Bug first reported by Keshav Kini.

Patch by Kaushik Phatak.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351673 91177308-0d34-0410-b5e6-96231b3b80d8