Have the rewriter check for CAPI excs directly

Previously it would have to call out to checkAndThrowCAPIException(),
which is quite a bit slower than what it now can do, which is directly
checking the return value.

src/asm_writing/rewriter.cpp

@@ -19,6 +19,7 @@
 #include "codegen/unwinding.h"
 #include "core/common.h"
 #include "core/stats.h"
+#include "runtime/types.h"
 
 namespace pyston {
 
@@ -1522,6 +1523,29 @@ void Rewriter::_allocateAndCopyPlus1(RewriterVar* result, RewriterVar* first_ele
     assertConsistent();
 }
 
+void Rewriter::checkAndThrowCAPIException(RewriterVar* r) {
+    STAT_TIMER(t0, "us_timer_rewriter", 10);
+
+    addAction([=]() { this->_checkAndThrowCAPIException(r); }, { r }, ActionType::MUTATION);
+}
+
+void Rewriter::_checkAndThrowCAPIException(RewriterVar* r) {
+    assembler->comment("_checkAndThrowCAPIException");
+
+    assembler::Register var_reg = r->getInReg();
+    assembler->test(var_reg, var_reg);
+
+    {
+        assembler::ForwardJump jnz(*assembler, assembler::COND_NOT_ZERO);
+        assembler->mov(assembler::Immediate((void*)throwCAPIException), assembler::R11);
+        assembler->callq(assembler::R11);
+    }
+
+    r->bumpUse();
+
+    assertConsistent();
+}
+
 assembler::Indirect Rewriter::indirectFor(Location l) {
     assert(l.type == Location::Scratch || l.type == Location::Stack);
 

src/asm_writing/rewriter.h

@@ -430,6 +430,7 @@ protected:
     int _allocate(RewriterVar* result, int n);
     void _allocateAndCopy(RewriterVar* result, RewriterVar* array, int n);
     void _allocateAndCopyPlus1(RewriterVar* result, RewriterVar* first_elem, RewriterVar* rest, int n_rest);
+    void _checkAndThrowCAPIException(RewriterVar* r);
 
     // The public versions of these are in RewriterVar
     void _addGuard(RewriterVar* var, RewriterVar* val_constant);
@@ -514,6 +515,9 @@ public:
     RewriterVar* allocateAndCopy(RewriterVar* array, int n);
     RewriterVar* allocateAndCopyPlus1(RewriterVar* first_elem, RewriterVar* rest, int n_rest);
 
+    // This emits `if (!r) throwCAPIException()`
+    void checkAndThrowCAPIException(RewriterVar* r);
+
     void abort();
     void commit();
     void commitReturning(RewriterVar* rtn);

src/runtime/objmodel.cpp

@@ -1375,8 +1375,7 @@ Box* dataDescriptorInstanceSpecialCases(GetattrRewriteArgs* rewrite_args, BoxedS
                 /* has_side_effects */ true, (void*)getset_descr->get, rewrite_args->obj, r_closure);
 
             if (descr->cls == capi_getset_cls)
-                // TODO I think we are supposed to check the return value?
-                rewrite_args->rewriter->call(true, (void*)checkAndThrowCAPIException);
+                rewrite_args->rewriter->checkAndThrowCAPIException(rewrite_args->out_rtn);
 
             rewrite_args->out_success = true;
         }
@@ -1434,7 +1433,7 @@ Box* getattrInternalEx(Box* obj, BoxedString* attr, GetattrRewriteArgs* rewrite_
                 auto r_rtn = rewrite_args->rewriter->call(true, (void*)obj->cls->tp_getattro, rewrite_args->obj, r_box);
 
                 if (S == CXX)
-                    rewrite_args->rewriter->call(true, (void*)checkAndThrowCAPIException);
+                    rewrite_args->rewriter->checkAndThrowCAPIException(r_rtn);
                 else
                     rewrite_args->rewriter->call(false, (void*)ensureValidCapiReturn, r_rtn);
 
@@ -3658,7 +3657,7 @@ Box* callCLFunc(CLFunction* f, CallRewriteArgs* rewrite_args, int num_output_arg
 
         rewrite_args->out_rtn = rewrite_args->rewriter->call(true, func_ptr, arg_vec);
         if (S == CXX && chosen_cf->exception_style == CAPI)
-            rewrite_args->rewriter->call(true, (void*)checkAndThrowCAPIException);
+            rewrite_args->rewriter->checkAndThrowCAPIException(rewrite_args->out_rtn);
 
         rewrite_args->out_success = true;
     }
@@ -4649,7 +4648,7 @@ Box* getitemInternal(Box* target, Box* slice, GetitemRewriteArgs* rewrite_args)
             r_m->addAttrGuard(offsetof(PyMappingMethods, mp_subscript), (intptr_t)m->mp_subscript);
             RewriterVar* r_rtn = rewrite_args->rewriter->call(true, (void*)m->mp_subscript, r_obj, r_slice);
             if (S == CXX)
-                rewrite_args->rewriter->call(true, (void*)checkAndThrowCAPIException);
+                rewrite_args->rewriter->checkAndThrowCAPIException(r_rtn);
             rewrite_args->out_success = true;
             rewrite_args->out_rtn = r_rtn;
         }