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Don't generate a branch hint for assertions in unoptimized builds #117367

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Don't generate a branch hint for assertions in unoptimized builds #117367

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9 changes: 6 additions & 3 deletions compiler/rustc_codegen_ssa/src/mir/block.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -573,7 +573,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
mergeable_succ: bool,
) -> MergingSucc {
let span = terminator.source_info.span;
let cond = self.codegen_operand(bx, cond).immediate();
let mut cond = self.codegen_operand(bx, cond).immediate();
let mut const_cond = bx.const_to_opt_u128(cond, false).map(|c| c == 1);

// This case can currently arise only from functions marked
Expand All @@ -589,8 +589,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
return helper.funclet_br(self, bx, target, mergeable_succ);
}

// Pass the condition through llvm.expect for branch hinting.
let cond = bx.expect(cond, expected);
// Give the backend a branch hint that hitting the assertion is unlikely,
// but only when optimizations are enabled.
if bx.tcx().sess.opts.optimize != OptLevel::No {
cond = bx.expect(cond, expected);
}

// Create the failure block and the conditional branch to it.
let lltarget = helper.llbb_with_cleanup(self, target);
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