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Unnecessary testl #10659

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llvmbot opened this issue Jul 6, 2011 · 3 comments
Closed

Unnecessary testl #10659

llvmbot opened this issue Jul 6, 2011 · 3 comments
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@majnemer
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backend:X86 bugzilla Issues migrated from bugzilla

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@llvmbot
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llvmbot commented Jul 6, 2011

Bugzilla Link 10287
Resolution FIXED
Resolved on May 15, 2013 18:44
Version trunk
OS All
Reporter LLVM Bugzilla Contributor
CC @lattner,@majnemer

Extended Description

given

double foobar(double x, int y) {
unsigned n = y;
double p = 1;
while (true) {
n >>= 1;
if (n == 0)
return p;
}
}

gcc produces:

__Z6foobardi:
shrl %edi
jne __Z6foobardi
movsd 0x00000004(%rip),%xmm0
re

clang produces:

__Z6foobardi:
shrl %edi
testl %edi,%edi
jne __Z6foobardi
movsd 0x00000002(%rip),%xmm0
ret
@llvmbot
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llvmbot commented Jul 6, 2011

assigned to @majnemer

@llvmbot
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llvmbot commented Aug 5, 2011

Hmm...This looks like a job for the Peephole optimizer pass in CodeGen. It's doing something similar for ARM.

@majnemer
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Mannequin

majnemer mannequin commented May 16, 2013

This is fixed in r181937.

foobar:
.LBB0_1:
shrl %edi
jne .LBB0_1
movsd .LCPI0_0(%rip), %xmm0
ret

@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 3, 2021
This issue was closed.
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