Revert "[Support] Refactor getN1Bits so it does not work around any g++ bug (llvm#78933)"

nikic · nikic · commit 15c8ba4c3b92 · 2024-05-27T08:38:23.000+02:00
This reverts commit bb02bf7. PR merged without review.
diff --git a/llvm/include/llvm/Support/Discriminator.h b/llvm/include/llvm/Support/Discriminator.h
@@ -121,9 +121,12 @@ static inline unsigned getBaseFSBitEnd() {
 }
 
 // Set bits in range of [0 .. n] to 1. Used in FS Discriminators.
-static inline unsigned getN1Bits(unsigned N) {
+static inline unsigned getN1Bits(int N) {
+  // Work around the g++ bug that folding "(1U << (N + 1)) - 1" to 0.
+  if (N == 31)
+    return 0xFFFFFFFF;
   assert((N < 32) && "N is invalid");
-  return 0xFFFFFFFF >> (31 - N);
+  return (1U << (N + 1)) - 1;
 }
 
 } // namespace llvm

Original file line number	Diff line number	Diff line change
`@@ -121,9 +121,12 @@ static inline unsigned getBaseFSBitEnd() {`
`121`	`121`	`}`
`122`	`122`
`123`	`123`	`// Set bits in range of [0 .. n] to 1. Used in FS Discriminators.`
`124`		`-static inline unsigned getN1Bits(unsigned N) {`
	`124`	`+static inline unsigned getN1Bits(int N) {`
	`125`	`+ // Work around the g++ bug that folding "(1U << (N + 1)) - 1" to 0.`
	`126`	`+ if (N == 31)`
	`127`	`+ return 0xFFFFFFFF;`
`125`	`128`	`assert((N < 32) && "N is invalid");`
`126`		`- return 0xFFFFFFFF >> (31 - N);`
	`129`	`+ return (1U << (N + 1)) - 1;`
`127`	`130`	`}`
`128`	`131`
`129`	`132`	`} // namespace llvm`