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// Available registers: r0, r1, r2 | |
// Source code | |
a = 1 | |
b = 1 | |
c = 1 | |
d = (a + b) + c | |
b = a + c | |
// SSA/Three-address code | |
a0 = 1 | |
b0 = 1 | |
c0 = 1 | |
t0 = a0 + b0 | |
d0 = t0 + c0 | |
b1 = a0 + c0 | |
// Liveness | |
// a0: [111111] | |
// b0: [011100] | |
// c0: [001111] | |
// t0: [000110] | |
// d0: [000010] | |
// b1: [000001] | |
// Linear scan results: | |
// a0 <- r0 | |
// b0 <- r1 | |
// c0 <- r2 | |
// t0 <- r0, a0 - spill | |
// d0 <- r1, b0 - expired | |
// b1 <- r0, t0, d0 - expired | |
// Pseudo-assembly | |
r0 <- 1 | |
r1 <- 1 | |
r2 <- 1 | |
st[0] <- r0 // spill | |
r0 <- st[0] // mov(st[0], r0) | |
r0 <- r0 + r1 // add(r1, r0) | |
r1 <- r0 // mov(r0, r1) | |
r1 <- r1 + r2 // add(r2, r1) | |
r0 <- st[0] // mov(st[0], r0) | |
r0 <- r0 + r2 // add(r2, r0) |
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