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Mips specific standalone assembler addressing mode %hi and %lo.

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The constructs %hi() and %lo() represent the high and low 16 
bits of the address. 
Because the 16 bit offset field of an LW instruction is 
interpreted as signed, if bit 15 of the low part is 1 then the 
low part will act as a negative and 1 needs to be added to the 
high part.

Contributer: Vladimir Medic


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175707 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jack Carter 2013-02-21 02:09:31 +00:00
parent 421021157e
commit 77217229ba
3 changed files with 18 additions and 3 deletions
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5
lib/Target/Mips/AsmParser/MipsAsmParser.cpp
View File

@ -888,7 +888,12 @@ bool MipsAsmParser::parseRelocOperand(const MCExpr *&Res) {
if (Str == "lo") {
Val = Val & 0xffff;
} else if (Str == "hi") {
int LoSign = Val & 0x8000;
Val = (Val & 0xffff0000) >> 16;
//lower part is treated as signed int, so if it is negative
//we must add 1 to hi part to compensate
if (LoSign)
Val++;
}
Res = MCConstantExpr::Create(Val, getContext());
return false;

11
test/MC/Mips/hilo-addressing.s Normal file
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@ -0,0 +1,11 @@
# RUN: llvm-mc -show-encoding -triple mips-unknown-unknown %s | FileCheck %s
.ent hilo_test
.equ addr, 0xdeadbeef
# CHECK: # encoding: [0x3c,0x04,0xde,0xae]
lui $4,%hi(addr)
# CHECK: # encoding: [0x03,0xe0,0x00,0x08]
jr $31
# CHECK: # encoding: [0x80,0x82,0xbe,0xef]
lb $2,%lo(addr)($4)
.end hilo_test

5
test/MC/Mips/mips_directives.s
View File

@ -1,5 +1,5 @@
# RUN: llvm-mc -triple mips-unknown-unknown %s | FileCheck %s
#this test produces no output so there isS no FileCheck call
# RUN: llvm-mc -show-encoding -triple mips-unknown-unknown %s | FileCheck %s
#
$BB0_2:
.ent directives_test
.frame $sp,0,$ra
@ -17,4 +17,3 @@ $JTI0_0:
.set macro
.set reorder
.set at=$a0
.end directives_test