Use 8-byte ops when loading/storing a TV type on the stack/frame local

Summary: This enables load/store pairs to the stack and locals -- both loads or stores have to have the same width to be combined into a single instruction.

Reviewed By: r1mikey

Differential Revision: D62789014

fbshipit-source-id: 8c619b6b8f63b7097056e1e2e1a6bbe781b2d458

hphp/runtime/vm/jit/code-gen-helpers.cpp

@@ -163,15 +163,19 @@ void storeTVVal(Vout& v, Type type, Vloc srcLoc, Vptr valPtr) {
 }
 
 void storeTVType(Vout& v, Type type, Vloc srcLoc, Vptr typePtr, bool aux) {
-  if (type.needsReg() || aux) {
+  if (type.needsReg()) {
     assertx(srcLoc.hasReg(1));
     if (aux) {
       v << store{srcLoc.reg(1), typePtr};
     } else {
       v << storeb{srcLoc.reg(1), typePtr};
     }
   } else {
-    v << storeb{v.cns(type.toDataType()), typePtr};
+    if (aux) {
+      v << store{v.cns(type.toDataType()), typePtr};
+    } else {
+      v << storeb{v.cns(type.toDataType()), typePtr};
+    }
   }
 }
 

hphp/runtime/vm/jit/irlower-load-store.cpp

@@ -76,7 +76,13 @@ void cgKillLoc(IRLS& env, const IRInstruction* inst) {
 void cgLdLoc(IRLS& env, const IRInstruction* inst) {
   auto const fp = srcLoc(env, inst, 0).reg();
   auto const off = localOffset(inst->extra<LdLoc>()->locId);
-  loadTV(vmain(env), inst->dst(), dstLoc(env, inst, 0), fp[off]);
+
+  // For ARM, if we need to load the type, then request 'aux' too -- even though
+  // the value is unneeded, it allows for the type and the value to be merged
+  // into a single loadpair.
+  const bool loadAux = arch() == Arch::ARM && inst->dst()->type().needsReg();
+
+  loadTV(vmain(env), inst->dst(), dstLoc(env, inst, 0), fp[off], loadAux);
 }
 
 void cgLdLocForeign(IRLS& env, const IRInstruction* inst) {
@@ -105,7 +111,14 @@ void cgLdLocAddr(IRLS& env, const IRInstruction* inst) {
 void cgStLoc(IRLS& env, const IRInstruction* inst) {
   auto const fp = srcLoc(env, inst, 0).reg();
   auto const off = localOffset(inst->extra<StLoc>()->locId);
-  storeTV(vmain(env), fp[off], srcLoc(env, inst, 1), inst->src(1));
+
+  // For ARM, we request the `aux' field to be stored too.  That's unused, but
+  // having a wider store for the type allows it to be merged with the store of
+  // the value into a single storepair instruction.
+  const bool storeAux = arch() == Arch::ARM;
+
+  storeTV(vmain(env), fp[off], srcLoc(env, inst, 1), inst->src(1),
+          TBottom, storeAux);
 }
 
 void cgStLocMeta(IRLS&, const IRInstruction*) {}
@@ -156,7 +169,13 @@ void cgDbgTrashFrame(IRLS& env, const IRInstruction* inst) {
 void cgLdStk(IRLS& env, const IRInstruction* inst) {
   auto const sp = srcLoc(env, inst, 0).reg();
   auto const off = cellsToBytes(inst->extra<LdStk>()->offset.offset);
-  loadTV(vmain(env), inst->dst(), dstLoc(env, inst, 0), sp[off]);
+
+  // For ARM, if we need to load the type, then request 'aux' too -- even though
+  // the value is unneeded, it allows for the type and the value to be merged
+  // into a single loadpair.
+  const bool loadAux = arch() == Arch::ARM && inst->dst()->type().needsReg();
+
+  loadTV(vmain(env), inst->dst(), dstLoc(env, inst, 0), sp[off], loadAux);
 }
 
 void cgLdStkAddr(IRLS& env, const IRInstruction* inst) {
@@ -173,7 +192,13 @@ void cgStStk(IRLS& env, const IRInstruction* inst) {
     ? inst->typeParam()
     : inst->src(1)->type();
 
-  storeTV(vmain(env), sp[off], srcLoc(env, inst, 1), inst->src(1), type);
+  // For ARM, we request the `aux' field to be stored too.  That's unused, but
+  // having a wider store for the type allows it to be merged with the store of
+  // the value into a single storepair instruction.
+  const bool storeAux = arch() == Arch::ARM;
+
+  storeTV(vmain(env), sp[off], srcLoc(env, inst, 1), inst->src(1), type,
+          storeAux);
 }
 
 void cgStStkMeta(IRLS&, const IRInstruction*) {}