From: Daniel Micay <danielmicay@gmail.com>
Date: Tue, 6 Aug 2013 21:44:40 +0000 (-0400)
Subject: add an intrinsic for inbounds GEP
X-Git-Url: https://git.lizzy.rs/?a=commitdiff_plain;h=7d115c94205dd4b937d29c77d1704aa3f801869e;p=rust.git

add an intrinsic for inbounds GEP
---

diff --git a/src/librustc/middle/trans/foreign.rs b/src/librustc/middle/trans/foreign.rs
index 5153296337d..b1e600b9d73 100644
--- a/src/librustc/middle/trans/foreign.rs
+++ b/src/librustc/middle/trans/foreign.rs
@@ -888,6 +888,11 @@ fn count_zeros_intrinsic(bcx: @mut Block, name: &'static str) {
             let offset = get_param(decl, first_real_arg + 1);
             Ret(bcx, GEP(bcx, ptr, [offset]));
         }
+        "offset_inbounds" => {
+            let ptr = get_param(decl, first_real_arg);
+            let offset = get_param(decl, first_real_arg + 1);
+            Ret(bcx, InBoundsGEP(bcx, ptr, [offset]));
+        }
         "memcpy32" => memcpy_intrinsic(bcx, "llvm.memcpy.p0i8.p0i8.i32", substs.tys[0], 32),
         "memcpy64" => memcpy_intrinsic(bcx, "llvm.memcpy.p0i8.p0i8.i64", substs.tys[0], 64),
         "memmove32" => memcpy_intrinsic(bcx, "llvm.memmove.p0i8.p0i8.i32", substs.tys[0], 32),
diff --git a/src/librustc/middle/trans/type_use.rs b/src/librustc/middle/trans/type_use.rs
index 42d5527ee43..ad83286c8c1 100644
--- a/src/librustc/middle/trans/type_use.rs
+++ b/src/librustc/middle/trans/type_use.rs
@@ -148,7 +148,8 @@ fn store_type_uses(cx: Context, fn_id: def_id) -> @~[type_uses] {
                     "visit_tydesc"  | "forget" | "frame_address" |
                     "morestack_addr" => 0,
 
-                    "offset" | "memcpy32" | "memcpy64" | "memmove32" | "memmove64" |
+                    "offset" | "offset_inbounds" |
+                    "memcpy32" | "memcpy64" | "memmove32" | "memmove64" |
                     "memset32" | "memset64" => use_repr,
 
                     "sqrtf32" | "sqrtf64" | "powif32" | "powif64" |
diff --git a/src/librustc/middle/typeck/check/mod.rs b/src/librustc/middle/typeck/check/mod.rs
index ea8a11fc7b3..8623ee546d6 100644
--- a/src/librustc/middle/typeck/check/mod.rs
+++ b/src/librustc/middle/typeck/check/mod.rs
@@ -3481,6 +3481,20 @@ fn param(ccx: @mut CrateCtxt, n: uint) -> ty::t {
                    mutbl: ast::m_imm
                }))
             }
+            "offset_inbounds" => {
+              (1,
+               ~[
+                  ty::mk_ptr(tcx, ty::mt {
+                      ty: param(ccx, 0),
+                      mutbl: ast::m_imm
+                  }),
+                  ty::mk_int()
+               ],
+               ty::mk_ptr(tcx, ty::mt {
+                   ty: param(ccx, 0),
+                   mutbl: ast::m_imm
+               }))
+            }
             "memcpy32" => {
               (1,
                ~[
diff --git a/src/libstd/ptr.rs b/src/libstd/ptr.rs
index dfd11f9227d..98fb132672c 100644
--- a/src/libstd/ptr.rs
+++ b/src/libstd/ptr.rs
@@ -272,6 +272,8 @@ pub trait RawPtr<T> {
     fn is_not_null(&self) -> bool;
     unsafe fn to_option(&self) -> Option<&T>;
     fn offset(&self, count: int) -> Self;
+    #[cfg(not(stage0))]
+    unsafe fn offset_inbounds(self, count: int) -> Self;
 }
 
 /// Extension methods for immutable pointers
@@ -304,6 +306,14 @@ unsafe fn to_option(&self) -> Option<&T> {
     /// Calculates the offset from a pointer.
     #[inline]
     fn offset(&self, count: int) -> *T { offset(*self, count) }
+
+    /// Calculates the offset from a pointer. The offset *must* be in-bounds of
+    /// the object, or one-byte-past-the-end.
+    #[inline]
+    #[cfg(not(stage0))]
+    unsafe fn offset_inbounds(self, count: int) -> *T {
+        intrinsics::offset_inbounds(self, count)
+    }
 }
 
 /// Extension methods for mutable pointers
@@ -336,6 +346,18 @@ unsafe fn to_option(&self) -> Option<&T> {
     /// Calculates the offset from a mutable pointer.
     #[inline]
     fn offset(&self, count: int) -> *mut T { mut_offset(*self, count) }
+
+    /// Calculates the offset from a pointer. The offset *must* be in-bounds of
+    /// the object, or one-byte-past-the-end. An arithmetic overflow is also
+    /// undefined behaviour.
+    ///
+    /// This method should be preferred over `offset` when the guarantee can be
+    /// satisfied, to enable better optimization.
+    #[inline]
+    #[cfg(not(stage0))]
+    unsafe fn offset_inbounds(self, count: int) -> *mut T {
+        intrinsics::offset_inbounds(self as *T, count) as *mut T
+    }
 }
 
 // Equality for pointers
diff --git a/src/libstd/unstable/intrinsics.rs b/src/libstd/unstable/intrinsics.rs
index 1270a80c354..c60edad3dbd 100644
--- a/src/libstd/unstable/intrinsics.rs
+++ b/src/libstd/unstable/intrinsics.rs
@@ -317,12 +317,21 @@ fn visit_leave_fn(&self, purity: uint, proto: uint,
     /// Get the address of the `__morestack` stack growth function.
     pub fn morestack_addr() -> *();
 
-    /// Adjust a pointer by an offset.
+    /// Calculates the offset from a pointer.
     ///
     /// This is implemented as an intrinsic to avoid converting to and from an
     /// integer, since the conversion would throw away aliasing information.
     pub fn offset<T>(dst: *T, offset: int) -> *T;
 
+    /// Calculates the offset from a pointer. The offset *must* be in-bounds of
+    /// the object, or one-byte-past-the-end. An arithmetic overflow is also
+    /// undefined behaviour.
+    ///
+    /// This intrinsic should be preferred over `offset` when the guarantee can
+    /// be satisfied, to enable better optimization.
+    #[cfg(not(stage0))]
+    pub fn offset_inbounds<T>(dst: *T, offset: int) -> *T;
+
     /// Equivalent to the `llvm.memcpy.p0i8.0i8.i32` intrinsic, with a size of
     /// `count` * `size_of::<T>()` and an alignment of `min_align_of::<T>()`
     pub fn memcpy32<T>(dst: *mut T, src: *T, count: u32);