Rollup merge of #142340 - RalfJung:miri-apfloat-mul-add, r=oli-obk

miri: we can use apfloat's mul_add now

With rust-lang/rustc_apfloat#11 fixed, there is no reason to still use host floats here.
Fixes rust-lang/miri#2995

We already have a test for this:
https://github.com/rust-lang/rust/blob/a7153db254acc387e271e75153bdbd3caa2bed89/src/tools/miri/tests/pass/float.rs#L998-L1003

r? ``@oli-obk``

Author: matthiaskrgr

Cargo.lock

@@ -3234,9 +3234,9 @@ dependencies = [
 
 [[package]]
 name = "rustc_apfloat"
-version = "0.2.2+llvm-462a31f5a5ab"
+version = "0.2.3+llvm-462a31f5a5ab"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "121e2195ff969977a4e2b5c9965ea867fce7e4cb5aee5b09dee698a7932d574f"
+checksum = "486c2179b4796f65bfe2ee33679acf0927ac83ecf583ad6c91c3b4570911b9ad"
 dependencies = [
  "bitflags",
  "smallvec",

src/tools/miri/src/intrinsics/mod.rs

@@ -272,8 +272,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let a = this.read_scalar(a)?.to_f32()?;
                 let b = this.read_scalar(b)?.to_f32()?;
                 let c = this.read_scalar(c)?.to_f32()?;
-                // FIXME: Using host floats, to work around https://github.com/rust-lang/rustc_apfloat/issues/11
-                let res = a.to_host().mul_add(b.to_host(), c.to_host()).to_soft();
+                let res = a.mul_add(b, c).value;
                 let res = this.adjust_nan(res, &[a, b, c]);
                 this.write_scalar(res, dest)?;
             }
@@ -282,8 +281,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let a = this.read_scalar(a)?.to_f64()?;
                 let b = this.read_scalar(b)?.to_f64()?;
                 let c = this.read_scalar(c)?.to_f64()?;
-                // FIXME: Using host floats, to work around https://github.com/rust-lang/rustc_apfloat/issues/11
-                let res = a.to_host().mul_add(b.to_host(), c.to_host()).to_soft();
+                let res = a.mul_add(b, c).value;
                 let res = this.adjust_nan(res, &[a, b, c]);
                 this.write_scalar(res, dest)?;
             }
@@ -295,8 +293,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let c = this.read_scalar(c)?.to_f32()?;
                 let fuse: bool = this.machine.rng.get_mut().random();
                 let res = if fuse {
-                    // FIXME: Using host floats, to work around https://github.com/rust-lang/rustc_apfloat/issues/11
-                    a.to_host().mul_add(b.to_host(), c.to_host()).to_soft()
+                    a.mul_add(b, c).value
                 } else {
                     ((a * b).value + c).value
                 };
@@ -310,8 +307,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let c = this.read_scalar(c)?.to_f64()?;
                 let fuse: bool = this.machine.rng.get_mut().random();
                 let res = if fuse {
-                    // FIXME: Using host floats, to work around https://github.com/rust-lang/rustc_apfloat/issues/11
-                    a.to_host().mul_add(b.to_host(), c.to_host()).to_soft()
+                    a.mul_add(b, c).value
                 } else {
                     ((a * b).value + c).value
                 };

src/tools/miri/src/intrinsics/simd.rs

@@ -320,7 +320,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                             let b = b.to_f32()?;
                             let c = c.to_f32()?;
                             let res = if fuse {
-                                a.to_host().mul_add(b.to_host(), c.to_host()).to_soft()
+                                a.mul_add(b, c).value
                             } else {
                                 ((a * b).value + c).value
                             };
@@ -332,7 +332,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                             let b = b.to_f64()?;
                             let c = c.to_f64()?;
                             let res = if fuse {
-                                a.to_host().mul_add(b.to_host(), c.to_host()).to_soft()
+                                a.mul_add(b, c).value
                             } else {
                                 ((a * b).value + c).value
                             };