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v8mips / v8mips

Port of Google v8 javascript engine to mips architecture
https://github.com/v8mips/v8mips/wiki
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cutest test-run-machops/RunUint32ModP failed #695

Open xwafish opened 5 years ago

xwafish commented 5 years ago

this case test 'Uint32Mod' which is compiled to divu and mfhi. see src/compiler/mips64/instruction-selector-mips64.cpp src/compiler/mips64/code-generator-mips64.cpp

this case failed when 0xffff ffff % 0xffff ffff

https://s3-eu-west-1.amazonaws.com/downloads-mips/documents/MD00087-2B-MIPS64BIS-AFP-05.04.pdf about div: Restrictions: If either GPR rt or GPR rs does not contain sign-extended 32-bit values (bits 63..31 equal), then the result of the operation is UNPREDICTABLE. If the divisor in GPR rt is zero, the arithmetic result value is UNPREDICTABLE.

here should use ddivu instead?

xwafish commented 5 years ago

function: unsigned mod(unsigned a, unsigned b)

unsigned a = 0xffff ffff; unsigned b = 0xffff ffff; if we call mod(a, b). when just enter function mod, the register 'a0' and 'a1' should be 0xffff ffff ffff ffff ffff? but the jited code generated by RawMachineAssembler is 0xffff ffff?

xwafish commented 5 years ago

sign extend the arguments will fix this issue.

do we need to fix this?