AArch64: Add folds to use new cbz/cbnz block terminators #9668
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We can fold sequences like this: testl w0, w0 jcc CC_E, label into a single, new opcode cbz w0, label if the flags set by testl are only used by the jcc operation. Not only does this reduce the number of instructions, but it also has the benefit of not clobbering the flags. On AArch64 the branch offset range for cbz/cbnz is identical to b.cc so there is no penalty for using them.
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We can fold sequences like this:
testl w0, w0
jcc CC_E, label
into a single, new opcode
cbz w0, label
if the flags set by testl are only used by the jcc operation. Not only does this reduce the number of instructions, but it also has the benefit of not clobbering the flags. On AArch64 the branch offset range for cbz/cbnz is identical to b.cc so there is no penalty for using them.