bjoernager/rust
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Auto merge of #77972 - Mark-Simulacrum:side-effect-loop, r=nagisa

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Prevent miscompilation in trivial loop {}

Ideally, we would want to handle a broader set of cases to fully fix the
underlying bug here. That is currently relatively expensive at compile and
runtime, so we don't do that for now.

Performance results indicate this is not a major regression, if at all, so it should be safe to land.

cc #28728
This commit is contained in:
bors 2020-10-16 14:06:37 +00:00
commit a78a62fc99
5 changed files with 42 additions and 9 deletions
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10
compiler/rustc_codegen_llvm/src/intrinsic.rs
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@ -334,8 +334,8 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
self.call(expect, &[cond, self.const_bool(expected)], None)
}
fn sideeffect(&mut self) {
if self.tcx.sess.opts.debugging_opts.insert_sideeffect {
fn sideeffect(&mut self, unconditional: bool) {
if unconditional || self.tcx.sess.opts.debugging_opts.insert_sideeffect {
let fnname = self.get_intrinsic(&("llvm.sideeffect"));
self.call(fnname, &[], None);
}
@ -390,7 +390,7 @@ fn codegen_msvc_try(
) {
let llfn = get_rust_try_fn(bx, &mut |mut bx| {
bx.set_personality_fn(bx.eh_personality());
bx.sideeffect();
bx.sideeffect(false);
let mut normal = bx.build_sibling_block("normal");
let mut catchswitch = bx.build_sibling_block("catchswitch");
@ -553,7 +553,7 @@ fn codegen_gnu_try(
// call %catch_func(%data, %ptr)
// ret 1
bx.sideeffect();
bx.sideeffect(false);
let mut then = bx.build_sibling_block("then");
let mut catch = bx.build_sibling_block("catch");
@ -615,7 +615,7 @@ fn codegen_emcc_try(
// call %catch_func(%data, %catch_data)
// ret 1
bx.sideeffect();
bx.sideeffect(false);
let mut then = bx.build_sibling_block("then");
let mut catch = bx.build_sibling_block("catch");