[llvm] [KnownFPClass] Improve KnownFPClass::toKnownBits deductions for IEEE types (PR #223204)

[Eric Ross via llvm-commits]

================
@@ -261,25 +435,70 @@ if.else:
   ret i1 false
 }
 
-define i32 @test_snan_only(float nofpclass(qnan sub norm zero inf) %x) {
+define i32 @test_snan_only(float nofpclass(qnan inf zero norm sub) %x) {
 ; CHECK-LABEL: @test_snan_only(
+; CHECK-NEXT:    ret i32 2139095040
+;
+  %y = bitcast float %x to i32
+  %and = and i32 %y, u0x7FC00000
+  ret i32 %and
+}
+
+define i32 @test_qnan_only(float nofpclass(snan inf zero norm sub) %x) {
+; CHECK-LABEL: @test_qnan_only(
+; CHECK-NEXT:    ret i32 2143289344
+;
+  %y = bitcast float %x to i32
+  %and = and i32 %y, u0x7FC00000
+  ret i32 %and
+}
+
+define i32 @test_nan_only_include_quiet_bit(float nofpclass(inf zero norm sub) %x) {
+; CHECK-LABEL: @test_nan_only_include_quiet_bit(
 ; CHECK-NEXT:    [[Y:%.*]] = bitcast float [[X:%.*]] to i32
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[Y]], 4194304
+; CHECK-NEXT:    [[AND:%.*]] = and i32 [[Y]], 2143289344
 ; CHECK-NEXT:    ret i32 [[AND]]
 ;
   %y = bitcast float %x to i32
-  %and = and i32 %y, 4194304
+  %and = and i32 %y, u0x7FC00000
   ret i32 %and
 }
 
-define i32 @test_qnan_only(float nofpclass(snan sub norm zero inf) %x) {
----------------
ZERICO2005 wrote:

The original `test_qnan_only` was renamed to `test_f32_quiet_bit_set`.

The original `test_snan_only` has been replaced by `test_f32_quiet_bit_clear`. I think this is fine, because  `test_f32_quiet_bit_clear` is able to make the exact same deductions with more limited `nofpclass` information (`nofpclass(qnan norm sub)` versus `nofpclass(qnan inf zero norm sub)`.


https://github.com/llvm/llvm-project/pull/223204