Simplify assert terminator only if condition evaluates to expected value

tmiasko · tmiasko · commit a9470d052236 · 2020-10-21T00:00:00.000Z
diff --git a/compiler/rustc_mir/src/transform/simplify_branches.rs b/compiler/rustc_mir/src/transform/simplify_branches.rs
@@ -49,9 +49,10 @@ impl<'tcx> MirPass<'tcx> for SimplifyBranches {
                 }
                 TerminatorKind::Assert {
                     target, cond: Operand::Constant(ref c), expected, ..
-                } if (c.literal.try_eval_bool(tcx, param_env) == Some(true)) == expected => {
-                    TerminatorKind::Goto { target }
-                }
+                } => match c.literal.try_eval_bool(tcx, param_env) {
+                    Some(v) if v == expected => TerminatorKind::Goto { target },
+                    _ => continue,
+                },
                 TerminatorKind::FalseEdge { real_target, .. } => {
                     TerminatorKind::Goto { target: real_target }
                 }

Original file line number	Diff line number	Diff line change
`@@ -49,9 +49,10 @@ impl<'tcx> MirPass<'tcx> for SimplifyBranches {`
`49`	`49`	`}`
`50`	`50`	`TerminatorKind::Assert {`
`51`	`51`	`target, cond: Operand::Constant(ref c), expected, ..`
`52`		`- } if (c.literal.try_eval_bool(tcx, param_env) == Some(true)) == expected => {`
`53`		`- TerminatorKind::Goto { target }`
`54`		`- }`
	`52`	`+ } => match c.literal.try_eval_bool(tcx, param_env) {`
	`53`	`+ Some(v) if v == expected => TerminatorKind::Goto { target },`
	`54`	`+ _ => continue,`
	`55`	`+ },`
`55`	`56`	`TerminatorKind::FalseEdge { real_target, .. } => {`
`56`	`57`	`TerminatorKind::Goto { target: real_target }`
`57`	`58`	`}`