Don't set `fast`(-math) for certain simd ops

`fast-math` implies things like functions not being able to accept as an
argument or return as a result, say, `inf` which made these functions
confusingly named or behaving incorrectly, depending on how you
interpret it. Since the time when these intrinsics have been implemented
the intrinsics user's (stdsimd) approach has changed significantly and
so now it is required that these intrinsics operate normally rather than
in "whatever" way.

Fixes #84268

3 files changed, 29 insertions, 31 deletions

diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 896e56a9a1e..f823792fabe 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -261,7 +261,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     fn fadd_fast(&mut self, lhs: &'ll Value, rhs: &'ll Value) -> &'ll Value {
         unsafe {
             let instr = llvm::LLVMBuildFAdd(self.llbuilder, lhs, rhs, UNNAMED);
-            llvm::LLVMRustSetHasUnsafeAlgebra(instr);
+            llvm::LLVMRustSetFastMath(instr);
             instr
         }
     }
@@ -269,7 +269,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     fn fsub_fast(&mut self, lhs: &'ll Value, rhs: &'ll Value) -> &'ll Value {
         unsafe {
             let instr = llvm::LLVMBuildFSub(self.llbuilder, lhs, rhs, UNNAMED);
-            llvm::LLVMRustSetHasUnsafeAlgebra(instr);
+            llvm::LLVMRustSetFastMath(instr);
             instr
         }
     }
@@ -277,7 +277,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     fn fmul_fast(&mut self, lhs: &'ll Value, rhs: &'ll Value) -> &'ll Value {
         unsafe {
             let instr = llvm::LLVMBuildFMul(self.llbuilder, lhs, rhs, UNNAMED);
-            llvm::LLVMRustSetHasUnsafeAlgebra(instr);
+            llvm::LLVMRustSetFastMath(instr);
             instr
         }
     }
@@ -285,7 +285,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     fn fdiv_fast(&mut self, lhs: &'ll Value, rhs: &'ll Value) -> &'ll Value {
         unsafe {
             let instr = llvm::LLVMBuildFDiv(self.llbuilder, lhs, rhs, UNNAMED);
-            llvm::LLVMRustSetHasUnsafeAlgebra(instr);
+            llvm::LLVMRustSetFastMath(instr);
             instr
         }
     }
@@ -293,7 +293,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     fn frem_fast(&mut self, lhs: &'ll Value, rhs: &'ll Value) -> &'ll Value {
         unsafe {
             let instr = llvm::LLVMBuildFRem(self.llbuilder, lhs, rhs, UNNAMED);
-            llvm::LLVMRustSetHasUnsafeAlgebra(instr);
+            llvm::LLVMRustSetFastMath(instr);
             instr
         }
     }
@@ -1242,14 +1242,14 @@ impl Builder<'a, 'll, 'tcx> {
     pub fn vector_reduce_fadd_fast(&mut self, acc: &'ll Value, src: &'ll Value) -> &'ll Value {
         unsafe {
             let instr = llvm::LLVMRustBuildVectorReduceFAdd(self.llbuilder, acc, src);
-            llvm::LLVMRustSetHasUnsafeAlgebra(instr);
+            llvm::LLVMRustSetFastMath(instr);
             instr
         }
     }
     pub fn vector_reduce_fmul_fast(&mut self, acc: &'ll Value, src: &'ll Value) -> &'ll Value {
         unsafe {
             let instr = llvm::LLVMRustBuildVectorReduceFMul(self.llbuilder, acc, src);
-            llvm::LLVMRustSetHasUnsafeAlgebra(instr);
+            llvm::LLVMRustSetFastMath(instr);
             instr
         }
     }
@@ -1282,7 +1282,7 @@ impl Builder<'a, 'll, 'tcx> {
         unsafe {
             let instr =
                 llvm::LLVMRustBuildVectorReduceFMin(self.llbuilder, src, /*NoNaNs:*/ true);
-            llvm::LLVMRustSetHasUnsafeAlgebra(instr);
+            llvm::LLVMRustSetFastMath(instr);
             instr
         }
     }
@@ -1290,7 +1290,7 @@ impl Builder<'a, 'll, 'tcx> {
         unsafe {
             let instr =
                 llvm::LLVMRustBuildVectorReduceFMax(self.llbuilder, src, /*NoNaNs:*/ true);
-            llvm::LLVMRustSetHasUnsafeAlgebra(instr);
+            llvm::LLVMRustSetFastMath(instr);
             instr
         }
     }
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 52fab2ea17d..fc6c1abf4af 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -1053,50 +1053,48 @@ fn generic_simd_intrinsic(
         let vec_ty = bx.type_vector(elem_ty, in_len);
 
         let (intr_name, fn_ty) = match name {
-            sym::simd_fsqrt => ("sqrt", bx.type_func(&[vec_ty], vec_ty)),
-            sym::simd_fsin => ("sin", bx.type_func(&[vec_ty], vec_ty)),
-            sym::simd_fcos => ("cos", bx.type_func(&[vec_ty], vec_ty)),
-            sym::simd_fabs => ("fabs", bx.type_func(&[vec_ty], vec_ty)),
             sym::simd_ceil => ("ceil", bx.type_func(&[vec_ty], vec_ty)),
-            sym::simd_floor => ("floor", bx.type_func(&[vec_ty], vec_ty)),
-            sym::simd_round => ("round", bx.type_func(&[vec_ty], vec_ty)),
-            sym::simd_trunc => ("trunc", bx.type_func(&[vec_ty], vec_ty)),
-            sym::simd_fexp => ("exp", bx.type_func(&[vec_ty], vec_ty)),
+            sym::simd_fabs => ("fabs", bx.type_func(&[vec_ty], vec_ty)),
+            sym::simd_fcos => ("cos", bx.type_func(&[vec_ty], vec_ty)),
             sym::simd_fexp2 => ("exp2", bx.type_func(&[vec_ty], vec_ty)),
+            sym::simd_fexp => ("exp", bx.type_func(&[vec_ty], vec_ty)),
             sym::simd_flog10 => ("log10", bx.type_func(&[vec_ty], vec_ty)),
             sym::simd_flog2 => ("log2", bx.type_func(&[vec_ty], vec_ty)),
             sym::simd_flog => ("log", bx.type_func(&[vec_ty], vec_ty)),
+            sym::simd_floor => ("floor", bx.type_func(&[vec_ty], vec_ty)),
+            sym::simd_fma => ("fma", bx.type_func(&[vec_ty, vec_ty, vec_ty], vec_ty)),
             sym::simd_fpowi => ("powi", bx.type_func(&[vec_ty, bx.type_i32()], vec_ty)),
             sym::simd_fpow => ("pow", bx.type_func(&[vec_ty, vec_ty], vec_ty)),
-            sym::simd_fma => ("fma", bx.type_func(&[vec_ty, vec_ty, vec_ty], vec_ty)),
+            sym::simd_fsin => ("sin", bx.type_func(&[vec_ty], vec_ty)),
+            sym::simd_fsqrt => ("sqrt", bx.type_func(&[vec_ty], vec_ty)),
+            sym::simd_round => ("round", bx.type_func(&[vec_ty], vec_ty)),
+            sym::simd_trunc => ("trunc", bx.type_func(&[vec_ty], vec_ty)),
             _ => return_error!("unrecognized intrinsic `{}`", name),
         };
-
         let llvm_name = &format!("llvm.{0}.v{1}{2}", intr_name, in_len, elem_ty_str);
         let f = bx.declare_cfn(&llvm_name, llvm::UnnamedAddr::No, fn_ty);
         let c = bx.call(f, &args.iter().map(|arg| arg.immediate()).collect::<Vec<_>>(), None);
-        unsafe { llvm::LLVMRustSetHasUnsafeAlgebra(c) };
         Ok(c)
     }
 
     if std::matches!(
         name,
-        sym::simd_fsqrt
-            | sym::simd_fsin
-            | sym::simd_fcos
+        sym::simd_ceil
             | sym::simd_fabs
-            | sym::simd_ceil
-            | sym::simd_floor
-            | sym::simd_round
-            | sym::simd_trunc
-            | sym::simd_fexp
+            | sym::simd_fcos
             | sym::simd_fexp2
+            | sym::simd_fexp
             | sym::simd_flog10
             | sym::simd_flog2
             | sym::simd_flog
-            | sym::simd_fpowi
-            | sym::simd_fpow
+            | sym::simd_floor
             | sym::simd_fma
+            | sym::simd_fpow
+            | sym::simd_fpowi
+            | sym::simd_fsin
+            | sym::simd_fsqrt
+            | sym::simd_round
+            | sym::simd_trunc
     ) {
         return simd_simple_float_intrinsic(name, in_elem, in_ty, in_len, bx, span, args);
     }
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 54a8249b175..32b1526f6e4 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -1354,7 +1354,7 @@ extern "C" {
     pub fn LLVMBuildNeg(B: &Builder<'a>, V: &'a Value, Name: *const c_char) -> &'a Value;
     pub fn LLVMBuildFNeg(B: &Builder<'a>, V: &'a Value, Name: *const c_char) -> &'a Value;
     pub fn LLVMBuildNot(B: &Builder<'a>, V: &'a Value, Name: *const c_char) -> &'a Value;
-    pub fn LLVMRustSetHasUnsafeAlgebra(Instr: &Value);
+    pub fn LLVMRustSetFastMath(Instr: &Value);
 
     // Memory
     pub fn LLVMBuildAlloca(B: &Builder<'a>, Ty: &'a Type, Name: *const c_char) -> &'a Value;