Use IRBuilder to create memset

To avoid creating memsets with outdated signature. For some reason
SROA chokes on this when using NewPM.

Author: nikic

src/librustc_codegen_llvm/builder.rs

@@ -781,13 +781,18 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         align: Align,
         flags: MemFlags,
     ) {
-        let ptr_width = &self.sess().target.target.target_pointer_width;
-        let intrinsic_key = format!("llvm.memset.p0i8.i{}", ptr_width);
-        let llintrinsicfn = self.get_intrinsic(&intrinsic_key);
+        let is_volatile = flags.contains(MemFlags::VOLATILE);
         let ptr = self.pointercast(ptr, self.type_i8p());
-        let align = self.const_u32(align.bytes() as u32);
-        let volatile = self.const_bool(flags.contains(MemFlags::VOLATILE));
-        self.call(llintrinsicfn, &[ptr, fill_byte, size, align, volatile], None);
+        unsafe {
+            llvm::LLVMRustBuildMemSet(
+                self.llbuilder,
+                ptr,
+                align.bytes() as c_uint,
+                fill_byte,
+                size,
+                is_volatile,
+            );
+        }
     }
 
     fn select(

src/librustc_codegen_llvm/context.rs

@@ -562,10 +562,6 @@ impl CodegenCx<'b, 'tcx> {
             t_v8f64: t_f64, 8;
         }
 
-        ifn!("llvm.memset.p0i8.i16", fn(i8p, t_i8, t_i16, t_i32, i1) -> void);
-        ifn!("llvm.memset.p0i8.i32", fn(i8p, t_i8, t_i32, t_i32, i1) -> void);
-        ifn!("llvm.memset.p0i8.i64", fn(i8p, t_i8, t_i64, t_i32, i1) -> void);
-
         ifn!("llvm.trap", fn() -> void);
         ifn!("llvm.debugtrap", fn() -> void);
         ifn!("llvm.frameaddress", fn(t_i32) -> i8p);

src/librustc_codegen_llvm/llvm/ffi.rs

@@ -1315,6 +1315,14 @@ extern "C" {
         Size: &'a Value,
         IsVolatile: bool,
     ) -> &'a Value;
+    pub fn LLVMRustBuildMemSet(
+        B: &Builder<'a>,
+        Dst: &'a Value,
+        DstAlign: c_uint,
+        Val: &'a Value,
+        Size: &'a Value,
+        IsVolatile: bool,
+    ) -> &'a Value;
     pub fn LLVMBuildSelect(
         B: &Builder<'a>,
         If: &'a Value,

src/rustllvm/RustWrapper.cpp

@@ -1296,6 +1296,14 @@ extern "C" LLVMValueRef LLVMRustBuildMemMove(LLVMBuilderRef B,
 #endif
 }
 
+extern "C" LLVMValueRef LLVMRustBuildMemSet(LLVMBuilderRef B,
+                                            LLVMValueRef Dst, unsigned DstAlign,
+                                            LLVMValueRef Val,
+                                            LLVMValueRef Size, bool IsVolatile) {
+  return wrap(unwrap(B)->CreateMemSet(
+      unwrap(Dst), unwrap(Val), unwrap(Size), DstAlign, IsVolatile));
+}
+
 extern "C" LLVMValueRef
 LLVMRustBuildInvoke(LLVMBuilderRef B, LLVMValueRef Fn, LLVMValueRef *Args,
                     unsigned NumArgs, LLVMBasicBlockRef Then,