Fix SFINAE in llvm::bit_cast.

[jlebar]

Summary

As far as I can tell, the SFINAE was broken; there is no such thing as
std::is_trivially_constructible<T>::type.

[jlebar]

Hm, thank you, arc, for including files that were not in my commit...

[jlebar]

Attempt to remove files which shouldn't be in here.

[jlebar]

arc is not cooperating; I'm going to delete this and create a new review. Sorry for the noise.

.ycm_extra_conf.py

+/Users/jlebar/code/conf/ycm-configs/llvm
 No newline at end of file

llvm/include/llvm/ADT/bit.h

 #include <cstring>
 #include <type_traits>
 
 namespace llvm {
 
 // This implementation of bit_cast is different from the C++17 one in two ways:
 //  - It isn't constexpr because that requires compiler support.
 //  - It requires trivially-constructible To, to avoid UB in the implementation.
-template <typename To, typename From
-          , typename = typename std::enable_if<sizeof(To) == sizeof(From)>::type
+template <
+    typename To, typename From,
+    typename = typename std::enable_if<sizeof(To) == sizeof(From)>::type
 #if (__has_feature(is_trivially_constructible) && defined(_LIBCPP_VERSION)) || \
     (defined(__GNUC__) && __GNUC__ >= 5)
-          , typename = typename std::is_trivially_constructible<To>::type
+    ,
+    typename = typename std::enable_if<
+        std::is_trivially_constructible<To>::value>::type
 #elif __has_feature(is_trivially_constructible)
-          , typename = typename std::enable_if<__is_trivially_constructible(To)>::type
+    ,
+    typename = typename std::enable_if<__is_trivially_constructible(To)>::type
 #else
   // See comment below.
 #endif
 #if (__has_feature(is_trivially_copyable) && defined(_LIBCPP_VERSION)) || \
     (defined(__GNUC__) && __GNUC__ >= 5)
-          , typename = typename std::enable_if<std::is_trivially_copyable<To>::value>::type
-          , typename = typename std::enable_if<std::is_trivially_copyable<From>::value>::type
+    ,
+    typename =
+        typename std::enable_if<std::is_trivially_copyable<To>::value>::type,
+    typename =
+        typename std::enable_if<std::is_trivially_copyable<From>::value>::type
 #elif __has_feature(is_trivially_copyable)
-          , typename = typename std::enable_if<__is_trivially_copyable(To)>::type
-          , typename = typename std::enable_if<__is_trivially_copyable(From)>::type
+    ,
+    typename = typename std::enable_if<__is_trivially_copyable(To)>::type,
+    typename = typename std::enable_if<__is_trivially_copyable(From)>::type
 #else
 // This case is GCC 4.x. clang with libc++ or libstdc++ never get here. Unlike
 // llvm/Support/type_traits.h's is_trivially_copyable we don't want to
 // provide a good-enough answer here: developers in that configuration will hit
 // compilation failures on the bots instead of locally. That's acceptable
 // because it's very few developers, and only until we move past C++11.
 #endif
     >
 inline To bit_cast(const From &from) noexcept {
   To to;
   std::memcpy(&to, &from, sizeof(To));
   return to;
 }
 
 } // namespace llvm
 
 #endif

testcases/mul.ll

+define i32 @test(i32 %x, i1 zeroext %b) {
+  %factor = select i1 %b, i32 8, i32 64
+  %ret = mul nsw i32 %x, %factor
+  ret i32 %ret
+}

testcases/run-test

+echo "core2"
+llvm-run llc < testcases/shift-regression.ll -mtriple=i386-apple-darwin10 --x86-asm-syntax=intel | llvm-run llvm-mca -mcpu=core2 |& grep '^Total Cycles'
+llvm-run llc < testcases/shift-regression.ll -mtriple=amd64-apple-darwin10 --x86-asm-syntax=intel | llvm-run llvm-mca -mcpu=core2 |& grep '^Total Cycles'
+
+echo "westmere"
+llvm-run llc < testcases/shift-regression.ll -mtriple=i386-apple-darwin10 --x86-asm-syntax=intel | llvm-run llvm-mca -mcpu=westmere |& grep '^Total Cycles'
+llvm-run llc < testcases/shift-regression.ll -mtriple=amd64-apple-darwin10 --x86-asm-syntax=intel | llvm-run llvm-mca -mcpu=westmere |& grep '^Total Cycles'
+
+echo "haswell"
+llvm-run llc < testcases/shift-regression.ll -mtriple=i386-apple-darwin10 --x86-asm-syntax=intel | llvm-run llvm-mca -mcpu=haswell |& grep '^Total Cycles'
+llvm-run llc < testcases/shift-regression.ll -mtriple=amd64-apple-darwin10 --x86-asm-syntax=intel | llvm-run llvm-mca -mcpu=haswell |& grep '^Total Cycles'

testcases/shift-regression.ll

+define i32 @trunc_select_miscompile(i32 %a, i1 zeroext %cc) {
+  %tmp1 = select i1 %cc, i32 3, i32 2
+  %tmp2 = shl i32 %a, %tmp1
+  ret i32 %tmp2
+}

testcases/shl.ll

+define i32 @foo(i32 %x, i1 zeroext %b) {
+  %factor = select i1 %b, i32 3, i32 6
+  %ret = shl i32 %x, %factor
+  ret i32 %ret
+}

testcases/shl2.ll

+define i32 @foo(i32 %x, i1 zeroext %cond) {
+  %a = shl i32 %x, 3
+  %b = shl i32 %x, 6
+  %ret = select i1 %cond, i32 %a, i32 %b
+  ret i32 %ret
+}