From d22e88ee7e4f1eab421c17f207cac89f19c721a3 Mon Sep 17 00:00:00 2001
From: Luca Bruno <lucab@debian.org>
Date: Sat, 24 Jan 2015 12:00:35 +0100
Subject: [PATCH 1/2] rustc_trans: don't hardcode llvm version for conditional
 intrinsics

This commit introduce a third parameter for compatible_ifn!, as new
intrinsics are being added in recent LLVM releases and there is no
need to hardcode a specific case.

Signed-off-by: Luca Bruno <lucab@debian.org>
---
 src/librustc_trans/trans/context.rs | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/src/librustc_trans/trans/context.rs b/src/librustc_trans/trans/context.rs
index e54962dc08552..c449bd7037cbf 100644
--- a/src/librustc_trans/trans/context.rs
+++ b/src/librustc_trans/trans/context.rs
@@ -874,11 +874,10 @@ fn declare_intrinsic(ccx: &CrateContext, key: & &'static str) -> Option<ValueRef
     ifn!("llvm.assume", fn(i1) -> void);
 
     // Some intrinsics were introduced in later versions of LLVM, but they have
-    // fallbacks in libc or libm and such. Currently, all of these intrinsics
-    // were introduced in LLVM 3.4, so we case on that.
+    // fallbacks in libc or libm and such.
     macro_rules! compatible_ifn {
-        ($name:expr, $cname:ident ($($arg:expr),*) -> $ret:expr) => (
-            if unsafe { llvm::LLVMVersionMinor() >= 4 } {
+        ($name:expr, $cname:ident ($($arg:expr),*) -> $ret:expr, $llvm_version:expr) => (
+            if unsafe { llvm::LLVMVersionMinor() >= $llvm_version } {
                 // The `if key == $name` is already in ifn!
                 ifn!($name, fn($($arg),*) -> $ret);
             } else if *key == $name {
@@ -891,10 +890,10 @@ fn declare_intrinsic(ccx: &CrateContext, key: & &'static str) -> Option<ValueRef
         )
     }
 
-    compatible_ifn!("llvm.copysign.f32", copysignf(t_f32, t_f32) -> t_f32);
-    compatible_ifn!("llvm.copysign.f64", copysign(t_f64, t_f64) -> t_f64);
-    compatible_ifn!("llvm.round.f32", roundf(t_f32) -> t_f32);
-    compatible_ifn!("llvm.round.f64", round(t_f64) -> t_f64);
+    compatible_ifn!("llvm.copysign.f32", copysignf(t_f32, t_f32) -> t_f32, 4);
+    compatible_ifn!("llvm.copysign.f64", copysign(t_f64, t_f64) -> t_f64, 4);
+    compatible_ifn!("llvm.round.f32", roundf(t_f32) -> t_f32, 4);
+    compatible_ifn!("llvm.round.f64", round(t_f64) -> t_f64, 4);
 
 
     if ccx.sess().opts.debuginfo != NoDebugInfo {

From 25f194ed46cbc622f84982dd7e00a9e3c2fae4f5 Mon Sep 17 00:00:00 2001
From: David Voit <david.voit@gmail.com>
Date: Sat, 23 May 2015 23:33:37 +0200
Subject: [PATCH 2/2] rustc_trans: 'assume' intrinsic is only available on LLVM
 >= 3.6

Based on the patch from Luca Bruno.

Instead of creating an empty C function in the rt, this version creates an shim
noop function using llvm. This function is declared as internal, and the
unsupported assume intrinsic and the shim gets completly removed by the
optimizer.
---
 src/librustc_trans/trans/context.rs | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/librustc_trans/trans/context.rs b/src/librustc_trans/trans/context.rs
index c449bd7037cbf..d4253f61ad0d1 100644
--- a/src/librustc_trans/trans/context.rs
+++ b/src/librustc_trans/trans/context.rs
@@ -871,11 +871,33 @@ fn declare_intrinsic(ccx: &CrateContext, key: & &'static str) -> Option<ValueRef
     ifn!("llvm.lifetime.end", fn(t_i64, i8p) -> void);
 
     ifn!("llvm.expect.i1", fn(i1, i1) -> i1);
-    ifn!("llvm.assume", fn(i1) -> void);
 
     // Some intrinsics were introduced in later versions of LLVM, but they have
     // fallbacks in libc or libm and such.
     macro_rules! compatible_ifn {
+        ($name:expr, noop($cname:ident ($($arg:expr),*) -> void), $llvm_version:expr) => (
+            if unsafe { llvm::LLVMVersionMinor() >= $llvm_version } {
+                // The `if key == $name` is already in ifn!
+                ifn!($name, fn($($arg),*) -> void);
+            } else if *key == $name {
+                let f = declare::declare_cfn(ccx, stringify!($cname),
+                                             Type::func(&[$($arg),*], &void),
+                                             ty::mk_nil(ccx.tcx()));
+                llvm::SetLinkage(f, llvm::InternalLinkage);
+
+                let bld = ccx.builder();
+                let llbb = unsafe {
+                    llvm::LLVMAppendBasicBlockInContext(ccx.llcx(), f,
+                                                        "entry-block\0".as_ptr() as *const _)
+                };
+
+                bld.position_at_end(llbb);
+                bld.ret_void();
+
+                ccx.intrinsics().borrow_mut().insert($name, f.clone());
+                return Some(f);
+            }
+        );
         ($name:expr, $cname:ident ($($arg:expr),*) -> $ret:expr, $llvm_version:expr) => (
             if unsafe { llvm::LLVMVersionMinor() >= $llvm_version } {
                 // The `if key == $name` is already in ifn!
@@ -894,6 +916,7 @@ fn declare_intrinsic(ccx: &CrateContext, key: & &'static str) -> Option<ValueRef
     compatible_ifn!("llvm.copysign.f64", copysign(t_f64, t_f64) -> t_f64, 4);
     compatible_ifn!("llvm.round.f32", roundf(t_f32) -> t_f32, 4);
     compatible_ifn!("llvm.round.f64", round(t_f64) -> t_f64, 4);
+    compatible_ifn!("llvm.assume", noop(llvmcompat_assume(i1) -> void), 6);
 
 
     if ccx.sess().opts.debuginfo != NoDebugInfo {