Optimization in SSA form (common

Static single assignment (SSA) form facilitates compiler optimizations. 1 Static single assignment form (SSA form) 1: a = x + y 2: a = a + 3 3: b = x + y Static single assignment (SSA) form (a) Normal (conventional) form (source program or internal form) 1: a1 = x0 + y0 2: a2 = a1 + 3 3: b1 = x0 + y0 (b) SSA form SSA form is a recently proposed internal representation where each use of a variable has a single definition point. Indices are attached to variables so that their definitions become unique. 1: a = x + y 2: a = a + 3 3: b = x + y Optimization in static single assignment (SSA) form (a) Normal form 1: a1 = x0 + y0 2: a2 = a1 + 3 3: b1 = x0 + y0 (b) SSA form 1: a1 = x0 + y0 2: a2 = a1 + 3 3: b1 = a1 (c) After SSA form optimization 1: a1 = x0 + y0 2: a2 = a1 + 3 3: b1 = a1 (d) Optimized normal form SSA translatio