Rollup merge of #54851 - alexcrichton:revert-optimize, r=sfackler
Rollup merge of #54851 - alexcrichton:revert-optimize, r=sfackler

Fix a regression in 1.30 by reverting #53564

Investigation on #54477 revealed https://github.com/rust-lang/rust/pull/53564 as the culprit in the regression for that crate. I've reproduced the regression with the [detailed test cases provided](https://github.com/rust-lang/rust/issues/54477#issuecomment-427398456). While we figure out how to fix the regression this commit reverts the current culprit.

graydon/rust,GBGamer/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust