Rollup merge of rust-lang#110494 - majaha:noTrapAfterNoreturn, r=nikic

TaKO8Ki · web-flow · commit 7a9bfd481c5b · 2023-06-27T22:47:02.000+09:00
Use the LLVM option NoTrapAfterNoreturn Use this LLVM option: https://llvm.org/doxygen/classllvm_1_1TargetOptions.html#acd83fce25de1ac9f6c975135a8235c22 when TrapUnreachable is enabled. This prevents codegenning unnecessary double-traps in some situations. See further discussion here: rust-lang/compiler-team#618
diff --git a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
@@ -437,6 +437,8 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
     // it prevents control flow from "falling through" into whatever code
     // happens to be laid out next in memory.
     Options.TrapUnreachable = true;
+    // But don't emit traps after other traps or no-returns unnecessarily.
+    Options.NoTrapAfterNoreturn = true;
   }
 
   if (Singlethread) {

Original file line number	Diff line number	Diff line change
`@@ -437,6 +437,8 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(`
`437`	`437`	`// it prevents control flow from "falling through" into whatever code`
`438`	`438`	`// happens to be laid out next in memory.`
`439`	`439`	`Options.TrapUnreachable = true;`
	`440`	`+ // But don't emit traps after other traps or no-returns unnecessarily.`
	`441`	`+ Options.NoTrapAfterNoreturn = true;`
`440`	`442`	`}`
`441`	`443`
`442`	`444`	`if (Singlethread) {`