Rollup merge of #91548 - luojia65:hint-spin-loop-riscv, r=Amanieu

matthiaskrgr · web-flow · commit 235693699e3f · 2021-12-11T15:44:27.000+01:00
Add spin_loop hint for RISC-V architecture This commit uses the PAUSE instruction (rust-lang/stdarch#1262) to implement RISC-V spin loop, and updates `stdarch` submodule to use the merged PAUSE instruction.
diff --git a/library/core/src/hint.rs b/library/core/src/hint.rs
@@ -137,6 +137,11 @@ pub fn spin_loop() {
             unsafe { crate::arch::arm::__yield() };
         }
     }
+
+    #[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))]
+    {
+        crate::arch::riscv::pause();
+    }
 }
 
 /// An identity function that *__hints__* to the compiler to be maximally pessimistic about what
diff --git a/library/stdarch b/library/stdarch
@@ -1 +1 @@
-Subproject commit cfba59fccd90b3b52a614120834320f764ab08d1
+Subproject commit b70ae88ef2a6c83acad0a1e83d5bd78f9655fd05

Original file line number	Diff line number	Diff line change
`@@ -137,6 +137,11 @@ pub fn spin_loop() {`
`137`	`137`	`unsafe { crate::arch::arm::__yield() };`
`138`	`138`	`}`
`139`	`139`	`}`
	`140`	`+`
	`141`	`+ #[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))]`
	`142`	`+ {`
	`143`	`+ crate::arch::riscv::pause();`
	`144`	`+ }`
`140`	`145`	`}`
`141`	`146`
`142`	`147`	`/// An identity function that __hints__ to the compiler to be maximally pessimistic about what`