[CIR] Generate SelectOp instead of TernaryOp for if cheap enough to evaluate unconditionally #1642
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…valuate unconditionally
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…valuate unconditionally (llvm#1642) This came up during the review of llvm/llvm-project#138156 During codegen we check whether the LHS and RHS of the conditional operator are cheap enough to evaluate uncondionally. Unlike classic codegen we still emit `TernaryOp` instead of `SelectOp` and defer that optimization to cir-simplify. This patch changes codegen to directly emit `SelectOp` for `cond ? constant : constant` expressions.
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This came up during the review of llvm/llvm-project#138156
During codegen we check whether the LHS and RHS of the conditional operator are cheap enough to evaluate uncondionally. Unlike classic codegen we still emit
TernaryOpinstead ofSelectOpand defer that optimization to cir-simplify.This patch changes codegen to directly emit
SelectOpforcond ? constant : constantexpressions.