[FMF] Set all bits if needed when setting individual flags. (#131321)

Currently fast() won't return true if all flags are set via setXXX,
which is surprising. Update setters to set all bits if needed to make
sure isFast() consistently returns the expected result.

PR: #131321

Author: fhahn

llvm/include/llvm/IR/FMF.h

@@ -23,13 +23,7 @@ class FastMathFlags {
 
   unsigned Flags = 0;
 
-  FastMathFlags(unsigned F) {
-    // If all 7 bits are set, turn this into -1. If the number of bits grows,
-    // this must be updated. This is intended to provide some forward binary
-    // compatibility insurance for the meaning of 'fast' in case bits are added.
-    if (F == 0x7F) Flags = ~0U;
-    else Flags = F;
-  }
+  FastMathFlags(unsigned F) : Flags(F) {}
 
 public:
   // This is how the bits are used in Value::SubclassOptionalData so they
@@ -43,9 +37,12 @@ class FastMathFlags {
     NoSignedZeros   = (1 << 3),
     AllowReciprocal = (1 << 4),
     AllowContract   = (1 << 5),
-    ApproxFunc      = (1 << 6)
+    ApproxFunc      = (1 << 6),
+    FlagEnd         = (1 << 7)
   };
 
+  constexpr static unsigned AllFlagsMask = FlagEnd - 1;
+
   FastMathFlags() = default;
 
   static FastMathFlags getFast() {
@@ -56,10 +53,10 @@ class FastMathFlags {
 
   bool any() const { return Flags != 0; }
   bool none() const { return Flags == 0; }
-  bool all() const { return Flags == ~0U; }
+  bool all() const { return Flags == AllFlagsMask; }
 
   void clear() { Flags = 0; }
-  void set()   { Flags = ~0U; }
+  void set() { Flags = AllFlagsMask; }
 
   /// Flag queries
   bool allowReassoc() const    { return 0 != (Flags & AllowReassoc); }

llvm/test/Transforms/LoopVectorize/AArch64/widen-call-with-intrinsic-or-libfunc.ll

@@ -26,7 +26,7 @@ target triple = "arm64-apple-ios"
 ; CHECK-NEXT:     vp<[[VEC_PTR:%.+]]> = vector-pointer ir<%gep.src>
 ; CHECK-NEXT:     WIDEN ir<%l> = load vp<[[VEC_PTR]]>
 ; CHECK-NEXT:     WIDEN-CAST ir<%conv> = fpext ir<%l> to double
-; CHECK-NEXT:     WIDEN-CALL ir<%s> = call reassoc nnan ninf nsz arcp contract afn @llvm.sin.f64(ir<%conv>) (using library function: __simd_sin_v2f64)
+; CHECK-NEXT:     WIDEN-CALL ir<%s> = call fast @llvm.sin.f64(ir<%conv>) (using library function: __simd_sin_v2f64)
 ; CHECK-NEXT:     REPLICATE ir<%gep.dst> = getelementptr inbounds ir<%dst>, vp<[[STEPS]]>
 ; CHECK-NEXT:     REPLICATE store ir<%s>, ir<%gep.dst>
 ; CHECK-NEXT:     EMIT vp<[[CAN_IV_NEXT:%.+]]> = add nuw vp<[[CAN_IV]]>, vp<[[VFxUF]]>
@@ -72,7 +72,7 @@ target triple = "arm64-apple-ios"
 ; CHECK-NEXT:     vp<[[VEC_PTR:%.+]]> = vector-pointer ir<%gep.src>
 ; CHECK-NEXT:     WIDEN ir<%l> = load vp<[[VEC_PTR]]>
 ; CHECK-NEXT:     WIDEN-CAST ir<%conv> = fpext ir<%l> to double
-; CHECK-NEXT:     WIDEN-INTRINSIC ir<%s> = call reassoc nnan ninf nsz arcp contract afn llvm.sin(ir<%conv>)
+; CHECK-NEXT:     WIDEN-INTRINSIC ir<%s> = call fast llvm.sin(ir<%conv>)
 ; CHECK-NEXT:     REPLICATE ir<%gep.dst> = getelementptr inbounds ir<%dst>, vp<[[STEPS]]>
 ; CHECK-NEXT:     REPLICATE store ir<%s>, ir<%gep.dst>
 ; CHECK-NEXT:     EMIT vp<[[CAN_IV_NEXT:%.+]]> = add nuw vp<[[CAN_IV]]>, vp<[[VFxUF]]>

llvm/test/Transforms/LoopVectorize/vplan-printing.ll

@@ -800,7 +800,7 @@ define void @print_fast_math_flags(i64 %n, ptr noalias %y, ptr noalias %x, ptr %
 ; CHECK-NEXT:   vp<[[VEC_PTR:%.+]]> = vector-pointer ir<%gep.y>
 ; CHECK-NEXT:   WIDEN ir<%lv> = load vp<[[VEC_PTR]]>
 ; CHECK-NEXT:   WIDEN ir<%add> = fadd nnan ir<%lv>, ir<1.000000e+00>
-; CHECK-NEXT:   WIDEN ir<%mul> = fmul reassoc nnan ninf nsz arcp contract afn ir<%add>, ir<2.000000e+00>
+; CHECK-NEXT:   WIDEN ir<%mul> = fmul fast ir<%add>, ir<2.000000e+00>
 ; CHECK-NEXT:   WIDEN ir<%div> = fdiv reassoc nsz contract ir<%mul>, ir<2.000000e+00>
 ; CHECK-NEXT:   CLONE ir<%gep.x> = getelementptr inbounds ir<%x>, vp<[[STEPS]]>
 ; CHECK-NEXT:   vp<[[VEC_PTR:%.+]]> = vector-pointer ir<%gep.x>
@@ -1224,8 +1224,8 @@ define void @print_select_with_fastmath_flags(ptr noalias %a, ptr noalias %b, pt
 ; CHECK-NEXT:     vp<[[PTR2:%.+]]> = vector-pointer ir<[[GEP2]]>
 ; CHECK-NEXT:     WIDEN ir<[[LD2:%.+]]> = load vp<[[PTR2]]>
 ; CHECK-NEXT:     WIDEN ir<[[FCMP:%.+]]> = fcmp ogt ir<[[LD1]]>, ir<[[LD2]]>
-; CHECK-NEXT:     WIDEN ir<[[FADD:%.+]]> = fadd reassoc nnan ninf nsz arcp contract afn ir<[[LD1]]>, ir<1.000000e+01>
-; CHECK-NEXT:     WIDEN-SELECT ir<[[SELECT:%.+]]> = select reassoc nnan ninf nsz arcp contract afn ir<[[FCMP]]>, ir<[[FADD]]>, ir<[[LD2]]>
+; CHECK-NEXT:     WIDEN ir<[[FADD:%.+]]> = fadd fast ir<[[LD1]]>, ir<1.000000e+01>
+; CHECK-NEXT:     WIDEN-SELECT ir<[[SELECT:%.+]]> = select fast ir<[[FCMP]]>, ir<[[FADD]]>, ir<[[LD2]]>
 ; CHECK-NEXT:     CLONE ir<[[GEP3:%.+]]> = getelementptr inbounds nuw ir<%a>, vp<[[ST]]>
 ; CHECK-NEXT:     vp<[[PTR3:%.+]]> = vector-pointer ir<[[GEP3]]>
 ; CHECK-NEXT:     WIDEN store vp<[[PTR3]]>, ir<[[SELECT]]>