Auto merge of #121223 - RalfJung:simd-intrinsics, r=Amanieu

intrinsics::simd: add missing functions, avoid UB-triggering fast-math

Turns out stdarch declares a bunch more SIMD intrinsics that are still missing from libcore.
I hope I got the docs and in particular the safety requirements right for these "unordered" and "nanless" intrinsics.

Many of these are unused even in stdarch, but they are implemented in the codegen backend, so we may as well list them here.

r? `@Amanieu`
Cc `@calebzulawski` `@workingjubilee`

3 files changed, 7 insertions, 25 deletions

diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index cfa266720d2..8cab2a3f27c 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -1367,17 +1367,17 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
     pub fn vector_reduce_fmul(&mut self, acc: &'ll Value, src: &'ll Value) -> &'ll Value {
         unsafe { llvm::LLVMRustBuildVectorReduceFMul(self.llbuilder, acc, src) }
     }
-    pub fn vector_reduce_fadd_algebraic(&mut self, acc: &'ll Value, src: &'ll Value) -> &'ll Value {
+    pub fn vector_reduce_fadd_reassoc(&mut self, acc: &'ll Value, src: &'ll Value) -> &'ll Value {
         unsafe {
             let instr = llvm::LLVMRustBuildVectorReduceFAdd(self.llbuilder, acc, src);
-            llvm::LLVMRustSetAlgebraicMath(instr);
+            llvm::LLVMRustSetAllowReassoc(instr);
             instr
         }
     }
-    pub fn vector_reduce_fmul_algebraic(&mut self, acc: &'ll Value, src: &'ll Value) -> &'ll Value {
+    pub fn vector_reduce_fmul_reassoc(&mut self, acc: &'ll Value, src: &'ll Value) -> &'ll Value {
         unsafe {
             let instr = llvm::LLVMRustBuildVectorReduceFMul(self.llbuilder, acc, src);
-            llvm::LLVMRustSetAlgebraicMath(instr);
+            llvm::LLVMRustSetAllowReassoc(instr);
             instr
         }
     }
@@ -1406,22 +1406,6 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
             llvm::LLVMRustBuildVectorReduceFMax(self.llbuilder, src, /*NoNaNs:*/ false)
         }
     }
-    pub fn vector_reduce_fmin_fast(&mut self, src: &'ll Value) -> &'ll Value {
-        unsafe {
-            let instr =
-                llvm::LLVMRustBuildVectorReduceFMin(self.llbuilder, src, /*NoNaNs:*/ true);
-            llvm::LLVMRustSetFastMath(instr);
-            instr
-        }
-    }
-    pub fn vector_reduce_fmax_fast(&mut self, src: &'ll Value) -> &'ll Value {
-        unsafe {
-            let instr =
-                llvm::LLVMRustBuildVectorReduceFMax(self.llbuilder, src, /*NoNaNs:*/ true);
-            llvm::LLVMRustSetFastMath(instr);
-            instr
-        }
-    }
     pub fn vector_reduce_min(&mut self, src: &'ll Value, is_signed: bool) -> &'ll Value {
         unsafe { llvm::LLVMRustBuildVectorReduceMin(self.llbuilder, src, is_signed) }
     }
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 3b091fca28b..23e6f054a7c 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -1880,14 +1880,14 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
     arith_red!(simd_reduce_mul_ordered: vector_reduce_mul, vector_reduce_fmul, true, mul, 1.0);
     arith_red!(
         simd_reduce_add_unordered: vector_reduce_add,
-        vector_reduce_fadd_algebraic,
+        vector_reduce_fadd_reassoc,
         false,
         add,
         0.0
     );
     arith_red!(
         simd_reduce_mul_unordered: vector_reduce_mul,
-        vector_reduce_fmul_algebraic,
+        vector_reduce_fmul_reassoc,
         false,
         mul,
         1.0
@@ -1920,9 +1920,6 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
     minmax_red!(simd_reduce_min: vector_reduce_min, vector_reduce_fmin);
     minmax_red!(simd_reduce_max: vector_reduce_max, vector_reduce_fmax);
 
-    minmax_red!(simd_reduce_min_nanless: vector_reduce_min, vector_reduce_fmin_fast);
-    minmax_red!(simd_reduce_max_nanless: vector_reduce_max, vector_reduce_fmax_fast);
-
     macro_rules! bitwise_red {
         ($name:ident : $red:ident, $boolean:expr) => {
             if name == sym::$name {
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index f9eb1da5dc7..dbf35e5f499 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -1619,6 +1619,7 @@ extern "C" {
 
     pub fn LLVMRustSetFastMath(Instr: &Value);
     pub fn LLVMRustSetAlgebraicMath(Instr: &Value);
+    pub fn LLVMRustSetAllowReassoc(Instr: &Value);
 
     // Miscellaneous instructions
     pub fn LLVMRustGetInstrProfIncrementIntrinsic(M: &Module) -> &Value;