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Tweak Thumb1 ADD encoding selection a bit.

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When the destination register of an add immediate instruction is
explicitly specified, encoding T1 is preferred, else encoding T2 is
preferred.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@138862 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jim Grosbach 2011-08-31 17:07:33 +00:00
parent 6154582983
commit 0f3abd8d68
2 changed files with 8 additions and 3 deletions
lib/Target/ARM/AsmParser
ARMAsmParser.cpp
test/MC/ARM
basic-thumb-instructions.s

7
lib/Target/ARM/AsmParser/ARMAsmParser.cpp

@ -3473,8 +3473,11 @@ processInstruction(MCInst &Inst,
}
break;
case ARM::tADDi8:
// If the immediate is in the range 0-7, we really wanted tADDi3.
if (Inst.getOperand(3).getImm() < 8)
// If the immediate is in the range 0-7, we want tADDi3 iff Rd was
// explicitly specified. From the ARM ARM: "Encoding T1 is preferred
// to encoding T2 if <Rd> is specified and encoding T2 is preferred
// to encoding T1 if <Rd> is omitted."
if (Inst.getOperand(3).getImm() < 8 && Operands.size() == 6)
Inst.setOpcode(ARM::tADDi3);
break;
case ARM::tBcc:

4
test/MC/ARM/basic-thumb-instructions.s

@ -26,11 +26,13 @@ _func:
@ ADD (immediate)
@------------------------------------------------------------------------------
adds r1, r2, #3
@ When Rd is not explicitly specified, encoding T2 is preferred even though
@ the literal is in the range [0,7] which would allow encoding T1.
adds r2, #3
adds r2, #8
@ CHECK: adds r1, r2, #3 @ encoding: [0xd1,0x1c]
@ CHECK: adds r2, r2, #3 @ encoding: [0xd2,0x1c]
@ CHECK: adds r2, #3 @ encoding: [0x03,0x32]
@ CHECK: adds r2, #8 @ encoding: [0x08,0x32]