Revision: 18688
Author: [email protected]
Date: Mon Jan 20 11:30:48 2014 UTC
Log: DoubleToIStub can't use ip on armv6, because the ubfx impl will
clobber it
This previous change broke DoubleToIStub on armv6:
https://code.google.com/p/v8/source/detail?r=16322
The problem is that DoubleToIStub::Generate assumed that it could safely
use the ip register, but on armv6 the ubfx implementation will clobber any
previous value stored there. So instead, pick another register.
Test case:
for (var i=0; i<2; i++) {
v = 4294967295;
v &= -2;
print(v)
}
This should print -2 twice, but on armv6 without this patch, it prints -2
followed by 2046.
This problem causes sunspider's bitops-nsieve-bit, crypto-md5 and
crypto-sha1 tests to generate incorrect results (but the results are not
checked for validity in sunspider-1.0 as available in chromium, but are
checked and reported as incorrect in sunspider-1.0.2).
Thanks to Tomasz Kilarski for helping out with this.
[email protected], [email protected]
Review URL: https://codereview.chromium.org/131823004
Patch from Mostyn Bramley-Moore <[email protected]>.
http://code.google.com/p/v8/source/detail?r=18688
Modified:
/branches/bleeding_edge/src/arm/code-stubs-arm.cc
=======================================
--- /branches/bleeding_edge/src/arm/code-stubs-arm.cc Wed Jan 15 17:00:35
2014 UTC
+++ /branches/bleeding_edge/src/arm/code-stubs-arm.cc Mon Jan 20 11:30:48
2014 UTC
@@ -665,17 +665,16 @@
int double_offset = offset();
// Account for saved regs if input is sp.
- if (input_reg.is(sp)) double_offset += 2 * kPointerSize;
+ if (input_reg.is(sp)) double_offset += 3 * kPointerSize;
- // Immediate values for this stub fit in instructions, so it's safe to
use ip.
- Register scratch = ip;
+ Register scratch = GetRegisterThatIsNotOneOf(input_reg, result_reg);
Register scratch_low =
GetRegisterThatIsNotOneOf(input_reg, result_reg, scratch);
Register scratch_high =
GetRegisterThatIsNotOneOf(input_reg, result_reg, scratch,
scratch_low);
LowDwVfpRegister double_scratch = kScratchDoubleReg;
- __ Push(scratch_high, scratch_low);
+ __ Push(scratch_high, scratch_low, scratch);
if (!skip_fastpath()) {
// Load double input.
@@ -758,7 +757,7 @@
__ bind(&done);
- __ Pop(scratch_high, scratch_low);
+ __ Pop(scratch_high, scratch_low, scratch);
__ Ret();
}
--
--
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