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Remove redundant load that is immediately after the store in same src/dst #35613
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[-]Remove redundant load that is followed by store[/-][+]Remove redundant load that is immediately after the store in same src/dst[/+]on Apr 29, 2020 Related: #35614
It turns out that we shouldn't do this optimization for 4-byte registers. Consider for below example, the 2nd instruction zero-extends the upper bits of
x0by doingldr. If 2nd instruction is eliminated, that won't be true and hence would cause functional bug.B90023A0 str w0, [fp,#32] // [V04 loc1] B94023A0 ldr w0, [fp,#32] // [V04 loc1]
With that, I re-calculated the patterns in framework libraries and looks like there are 1442 patterns in 830 methods.
Details:
str-ldr-x.txt- ghost locked as resolved and limited conversation to collaborators
on Dec 9, 2020
I have seen below pattern in generated code for framework libraries. We can eliminate the
ldrif it is loading the value into same register that was used to store in previous instruction in same memory location.Example of ARM64 code:
Example of x64 code:
There are approx. 2500 such patterns in 1500 methods. Details in str-ldr.txt.
category:cq
theme:basic-cq
skill-level:intermediate
cost:medium