[LLVMbugs] [Bug 11260] New: Fold ADCS Rd, Rn, Rm to ADCS Rdn, Rm when d=n and .W not specified
bugzilla-daemon at llvm.org
bugzilla-daemon at llvm.org
Fri Oct 28 12:42:25 PDT 2011
http://llvm.org/bugs/show_bug.cgi?id=11260
Summary: Fold ADCS Rd, Rn, Rm to ADCS Rdn, Rm when d=n and .W
not specified
Product: libraries
Version: trunk
Platform: PC
OS/Version: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: ARM
AssignedTo: unassignedbugs at nondot.org
ReportedBy: xocotl at gmail.com
CC: llvmbugs at cs.uiuc.edu
Very minor feature suggestion:
I caught this while looking at the output of some Thumb 2 inline assembler.
ADCS Rd, Rn, Rm was encoded in wide form
...
44: f7ff fffe bl 0 <s32_ufract_mul>
48: 182d adds r5, r5, r0
4a: eb54 0401 adcs.w r4, r4, r1
4e: bf64 itt vs
50: 17e5 asrvs r5, r4, #31
...
The original inline assembler was
...
"adds %Q0, %Q0, %Q1\n"
"adcs %R0, %R0, %R1\n"
"itt vs\n"
...
GCC folded this to the narrow form.
Granted in this particular case (porting it over from GCC), I could have just
used the two-argument, but what if I hadn't? If it folded after register
assignment into 16-bit forms where possible, this could save code space.
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