AuroraMiddleware/v8
1
0
Fork 0
Code Issues 2 Pull Requests Releases Wiki Activity

[turbofan][x64] Make ChangeUint32ToUint64 a Nop after Load(kWord32)

Browse Source 
A Load(kWord32) generates a movl instruction, which clears the high word
of a register already.

R=bmeurer@chromium.org

Change-Id: I835e5549483043a3faea08a1223070514f634c9e
Reviewed-on: https://chromium-review.googlesource.com/729863
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48777}
This commit is contained in:
Andreas Haas 2017-10-20 10:37:22 +02:00 committed by Commit Bot
parent a00a91426d
commit bd9bd17dbf
1 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
src/compiler/x64/instruction-selector-x64.cc
View File

@ -1242,13 +1242,13 @@ bool ZeroExtendsWord32ToWord64(Node* node) {
}
}
case IrOpcode::kLoad: {
// The movzxbl/movsxbl/movzxwl/movsxwl operations implicitly zero-extend
// to 64-bit on x64,
// so the zero-extension is a no-op.
// The movzxbl/movsxbl/movzxwl/movsxwl/movl operations implicitly
// zero-extend to 64-bit on x64, so the zero-extension is a no-op.
LoadRepresentation load_rep = LoadRepresentationOf(node->op());
switch (load_rep.representation()) {
case MachineRepresentation::kWord8:
case MachineRepresentation::kWord16:
case MachineRepresentation::kWord32:
return true;
default:
return false;