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Call instructions no longer have a list of 43 call-clobbered registers. Instead, they get a single register mask operand with a bit vector of call-preserved registers. This saves a lot of memory, 42 x 32 bytes = 1344 bytes per call instruction, and it speeds up building call instructions because those 43 imp-def operands no longer need to be added to use-def lists. (And removed and shifted and re-added for every explicit call operand). Passes like LiveVariables, LiveIntervals, RAGreedy, PEI, and BranchFolding are significantly faster because they can deal with call clobbers in bulk. Overall, clang -O2 is between 0% and 8% faster, uniformly distributed depending on call density in the compiled code. Debug builds using clang -O0 are 0% - 3% faster. I have verified that this patch doesn't change the assembly generated for the LLVM nightly test suite when building with -disable-copyprop and -disable-branch-fold. Branch folding behaves slightly differently in a few cases because call instructions have different hash values now. Copy propagation flushes its data structures when it crosses a register mask operand. This causes it to leave a few dead copies behind, on the order of 20 instruction across the entire nightly test suite, including SPEC. Fixing this properly would require the pass to use different data structures. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150638 91177308-0d34-0410-b5e6-96231b3b80d8 |
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AsmParser | ||
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CodeGen | ||
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TableGen | ||
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