Title: [173205] trunk/Source/_javascript_Core
- Revision
- 173205
- Author
- [email protected]
- Date
- 2014-09-03 07:15:09 -0700 (Wed, 03 Sep 2014)
Log Message
Don't generate superfluous mov instructions for move immediate on ARM64.
https://bugs.webkit.org/show_bug.cgi?id=136435
Patch by Akos Kiss <[email protected]> on 2014-09-03
Reviewed by Michael Saboff.
On ARM64, the size of an immediate operand for a mov instruction is 16
bits. Thus, a move immediate offlineasm instruction may potentially be
split up to several machine level instructions. The current
implementation always emits a mov for the least significant 16 bits of
the value. However, if any of the bits 63:16 are significant then the
first emitted mov already filled bits 15:0 with zeroes (or ones, for
negative values). So, if bits 15:0 of the value are all zeroes (or ones)
then the last mov does not need to be emitted.
* offlineasm/arm64.rb:
Modified Paths
Diff
Modified: trunk/Source/_javascript_Core/ChangeLog (173204 => 173205)
--- trunk/Source/_javascript_Core/ChangeLog 2014-09-03 12:45:12 UTC (rev 173204)
+++ trunk/Source/_javascript_Core/ChangeLog 2014-09-03 14:15:09 UTC (rev 173205)
@@ -1,3 +1,21 @@
+2014-09-03 Akos Kiss <[email protected]>
+
+ Don't generate superfluous mov instructions for move immediate on ARM64.
+ https://bugs.webkit.org/show_bug.cgi?id=136435
+
+ Reviewed by Michael Saboff.
+
+ On ARM64, the size of an immediate operand for a mov instruction is 16
+ bits. Thus, a move immediate offlineasm instruction may potentially be
+ split up to several machine level instructions. The current
+ implementation always emits a mov for the least significant 16 bits of
+ the value. However, if any of the bits 63:16 are significant then the
+ first emitted mov already filled bits 15:0 with zeroes (or ones, for
+ negative values). So, if bits 15:0 of the value are all zeroes (or ones)
+ then the last mov does not need to be emitted.
+
+ * offlineasm/arm64.rb:
+
2014-09-02 Brian J. Burg <[email protected]>
LegacyProfiler: remove redundant ProfileNode members and other cleanup
Modified: trunk/Source/_javascript_Core/offlineasm/arm64.rb (173204 => 173205)
--- trunk/Source/_javascript_Core/offlineasm/arm64.rb 2014-09-03 12:45:12 UTC (rev 173204)
+++ trunk/Source/_javascript_Core/offlineasm/arm64.rb 2014-09-03 14:15:09 UTC (rev 173205)
@@ -369,7 +369,7 @@
[48, 32, 16, 0].each {
| shift |
currentValue = (value >> shift) & 0xffff
- next if currentValue == (isNegative ? 0xffff : 0) and shift != 0
+ next if currentValue == (isNegative ? 0xffff : 0) and (shift != 0 or !first)
if first
if isNegative
$asm.puts "movn #{target.arm64Operand(:ptr)}, \##{(~currentValue) & 0xffff}, lsl \##{shift}"
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