Auto merge of #35261 - eddyb:llvm-autoupgrade, r=nikomatsakis

Support removed LLVM intrinsics by invoking its AutoUpgrade mechanism.

Turns out that LLVM sometimes renames platform intrinsics or replaces them with first-class instructions.
For example, signed minimum became `select (icmp SLT, a, b), a, b` where `a` and `b` are vectors.

This is blocking the Servo rustup ([relevant failure](http://build.servo.org/builders/windows-dev/builds/226/steps/compile/logs/stdio)), as they're using a few such intrinsics.
The fix in this PR is to invoke LLVM's own `AutoUpgrade` mechanism to do the replacements.

Author: bors

src/rustllvm/PassWrapper.cpp

@@ -17,6 +17,7 @@
 #include "llvm/Support/Host.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/IR/AutoUpgrade.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetSubtargetInfo.h"
 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
@@ -361,10 +362,17 @@ extern "C" void
 LLVMRustRunFunctionPassManager(LLVMPassManagerRef PM, LLVMModuleRef M) {
     llvm::legacy::FunctionPassManager *P = unwrap<llvm::legacy::FunctionPassManager>(PM);
     P->doInitialization();
+
+    // Upgrade all calls to old intrinsics first.
+    for (Module::iterator I = unwrap(M)->begin(),
+         E = unwrap(M)->end(); I != E;)
+        UpgradeCallsToIntrinsic(&*I++); // must be post-increment, as we remove
+
     for (Module::iterator I = unwrap(M)->begin(),
          E = unwrap(M)->end(); I != E; ++I)
         if (!I->isDeclaration())
             P->run(*I);
+
     P->doFinalization();
 }
 

src/test/run-pass/simd-upgraded.rs

@@ -0,0 +1,30 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Test that removed LLVM SIMD intrinsics continue
+// to work via the "AutoUpgrade" mechanism.
+
+#![feature(cfg_target_feature, repr_simd)]
+#![feature(platform_intrinsics, stmt_expr_attributes)]
+
+#[repr(simd)]
+#[derive(PartialEq, Debug)]
+struct i16x8(i16, i16, i16, i16, i16, i16, i16, i16);
+
+fn main() {
+    #[cfg(target_feature = "sse2")] unsafe {
+        extern "platform-intrinsic" {
+            fn x86_mm_min_epi16(x: i16x8, y: i16x8) -> i16x8;
+        }
+        assert_eq!(x86_mm_min_epi16(i16x8(0, 1, 2, 3, 4, 5, 6, 7),
+                                    i16x8(7, 6, 5, 4, 3, 2, 1, 0)),
+                                    i16x8(0, 1, 2, 3, 3, 2, 1, 0));
+    };
+}