search for: dsu1wi

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2019 Oct 25
4
unnecessary reload of 8-byte struct on i386
Hello folks, I've recently been looking at the generated code for a few functions in Chromium while investigating crashes, and I came across a curious pattern. A smallish repro case is available at https://godbolt.org/z/Dsu1WI . In that case, the function Assembler::emit_arith receives a struct (Operand) by value and passes it by value to another function. That struct is 8 bytes long, so the -O3 generated code uses movsd to copy it up the stack. However, we end up with some loads that aren't needed, as in the followi...