[clang] [clang] Use constant rounding mode for floating literals (PR #90877)

[Erich Keane via cfe-commits]

================
@@ -79,3 +79,16 @@ float V7 = []() -> float {
   0x0.000001p0F);
 }();
 // CHECK: @V7 = {{.*}} float 1.000000e+00
+
+template<float V> struct L {
+  constexpr L() : value(V) {}
+  float value;
+};
+
+#pragma STDC FENV_ROUND FE_DOWNWARD
----------------
erichkeane wrote:

I meant something like:

``` template<typename T, T V> void foo() {
#pragma STDC FENV_ROUND FE_DOWNWARD
T Val = V;
// Should be:  { float 0x3FB9999980000000 }
}
#pragma STDC FENV_ROUND FE_UPDWARD
foo<float, 0.1F>();


https://github.com/llvm/llvm-project/pull/90877