Rollup merge of #62828 - nikic:fadd-mul-reductions, r=eddyb

Remove vector fadd/fmul reduction workarounds

The bugs that this was working around have been fixed in LLVM 9.

r? @gnzlbg

4 files changed, 11 insertions, 50 deletions

diff --git a/src/librustc_codegen_llvm/builder.rs b/src/librustc_codegen_llvm/builder.rs
index 5ac1cf8c36f..894e5c2fd3d 100644
--- a/src/librustc_codegen_llvm/builder.rs
+++ b/src/librustc_codegen_llvm/builder.rs
@@ -1153,11 +1153,14 @@ impl Builder<'a, 'll, 'tcx> {
         }
     }
 
+    pub fn vector_reduce_fadd(&mut self, acc: &'ll Value, src: &'ll Value) -> &'ll Value {
+        unsafe { llvm::LLVMRustBuildVectorReduceFAdd(self.llbuilder, acc, src) }
+    }
+    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_fast(&mut self, acc: &'ll Value, src: &'ll Value) -> &'ll Value {
         unsafe {
-            // FIXME: add a non-fast math version once
-            // https://bugs.llvm.org/show_bug.cgi?id=36732
-            // is fixed.
             let instr = llvm::LLVMRustBuildVectorReduceFAdd(self.llbuilder, acc, src);
             llvm::LLVMRustSetHasUnsafeAlgebra(instr);
             instr
@@ -1165,9 +1168,6 @@ impl Builder<'a, 'll, 'tcx> {
     }
     pub fn vector_reduce_fmul_fast(&mut self, acc: &'ll Value, src: &'ll Value) -> &'ll Value {
         unsafe {
-            // FIXME: add a non-fast math version once
-            // https://bugs.llvm.org/show_bug.cgi?id=36732
-            // is fixed.
             let instr = llvm::LLVMRustBuildVectorReduceFMul(self.llbuilder, acc, src);
             llvm::LLVMRustSetHasUnsafeAlgebra(instr);
             instr
diff --git a/src/librustc_codegen_llvm/common.rs b/src/librustc_codegen_llvm/common.rs
index e9f25e6344b..f00624f3811 100644
--- a/src/librustc_codegen_llvm/common.rs
+++ b/src/librustc_codegen_llvm/common.rs
@@ -166,25 +166,6 @@ impl CodegenCx<'ll, 'tcx> {
             r
         }
     }
-
-    pub fn const_get_real(&self, v: &'ll Value) -> Option<(f64, bool)> {
-        unsafe {
-            if self.is_const_real(v) {
-                let mut loses_info: llvm::Bool = 0;
-                let r = llvm::LLVMConstRealGetDouble(v, &mut loses_info);
-                let loses_info = if loses_info == 1 { true } else { false };
-                Some((r, loses_info))
-            } else {
-                None
-            }
-        }
-    }
-
-    fn is_const_real(&self, v: &'ll Value) -> bool {
-        unsafe {
-            llvm::LLVMIsAConstantFP(v).is_some()
-        }
-    }
 }
 
 impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
diff --git a/src/librustc_codegen_llvm/intrinsic.rs b/src/librustc_codegen_llvm/intrinsic.rs
index dd6cfd7e29e..44b3eff2ac5 100644
--- a/src/librustc_codegen_llvm/intrinsic.rs
+++ b/src/librustc_codegen_llvm/intrinsic.rs
@@ -1640,29 +1640,11 @@ fn generic_simd_intrinsic(
                         }
                     },
                     ty::Float(f) => {
-                        // ordered arithmetic reductions take an accumulator
                         let acc = if $ordered {
-                            let acc = args[1].immediate();
-                            // FIXME: https://bugs.llvm.org/show_bug.cgi?id=36734
-                            // * if the accumulator of the fadd isn't 0, incorrect
-                            //   code is generated
-                            // * if the accumulator of the fmul isn't 1, incorrect
-                            //   code is generated
-                            match bx.const_get_real(acc) {
-                                None => return_error!("accumulator of {} is not a constant", $name),
-                                Some((v, loses_info)) => {
-                                    if $name.contains("mul") && v != 1.0_f64 {
-                                        return_error!("accumulator of {} is not 1.0", $name);
-                                    } else if $name.contains("add") && v != 0.0_f64 {
-                                        return_error!("accumulator of {} is not 0.0", $name);
-                                    } else if loses_info {
-                                        return_error!("accumulator of {} loses information", $name);
-                                    }
-                                }
-                            }
-                            acc
+                            // ordered arithmetic reductions take an accumulator
+                            args[1].immediate()
                         } else {
-                            // unordered arithmetic reductions do not:
+                            // unordered arithmetic reductions use the identity accumulator
                             let identity_acc = if $name.contains("mul") { 1.0 } else { 0.0 };
                             match f.bit_width() {
                                 32 => bx.const_real(bx.type_f32(), identity_acc),
@@ -1688,8 +1670,8 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
         }
     }
 
-    arith_red!("simd_reduce_add_ordered": vector_reduce_add, vector_reduce_fadd_fast, true);
-    arith_red!("simd_reduce_mul_ordered": vector_reduce_mul, vector_reduce_fmul_fast, true);
+    arith_red!("simd_reduce_add_ordered": vector_reduce_add, vector_reduce_fadd, true);
+    arith_red!("simd_reduce_mul_ordered": vector_reduce_mul, vector_reduce_fmul, true);
     arith_red!("simd_reduce_add_unordered": vector_reduce_add, vector_reduce_fadd_fast, false);
     arith_red!("simd_reduce_mul_unordered": vector_reduce_mul, vector_reduce_fmul_fast, false);
 
diff --git a/src/librustc_codegen_llvm/llvm/ffi.rs b/src/librustc_codegen_llvm/llvm/ffi.rs
index 5d82698d8ef..8c6ea00eb8c 100644
--- a/src/librustc_codegen_llvm/llvm/ffi.rs
+++ b/src/librustc_codegen_llvm/llvm/ffi.rs
@@ -719,7 +719,6 @@ extern "C" {
     pub fn LLVMConstIntGetZExtValue(ConstantVal: &Value) -> c_ulonglong;
     pub fn LLVMRustConstInt128Get(ConstantVal: &Value, SExt: bool,
                                   high: &mut u64, low: &mut u64) -> bool;
-    pub fn LLVMConstRealGetDouble (ConstantVal: &Value, losesInfo: &mut Bool) -> f64;
 
 
     // Operations on composite constants
@@ -1663,7 +1662,6 @@ extern "C" {
     pub fn LLVMRustWriteValueToString(value_ref: &Value, s: &RustString);
 
     pub fn LLVMIsAConstantInt(value_ref: &Value) -> Option<&Value>;
-    pub fn LLVMIsAConstantFP(value_ref: &Value) -> Option<&Value>;
 
     pub fn LLVMRustPassKind(Pass: &Pass) -> PassKind;
     pub fn LLVMRustFindAndCreatePass(Pass: *const c_char) -> Option<&'static mut Pass>;