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0fa193b086
The ldr-pseudo opcode is a convenience for loading 32-bit constants.
It is converted into a pc-relative load from a constant pool. For
example,
ldr r0, =0x10001
ldr r1, =bar
will generate this output in the final assembly
ldr r0, .Ltmp0
ldr r1, .Ltmp1
...
.Ltmp0: .long 0x10001
.Ltmp1: .long bar
Sketch of the LDR pseudo implementation:
Keep a map from Section => ConstantPool
When parsing ldr r0, =val
parse val as an MCExpr
get ConstantPool for current Section
Label = CreateTempSymbol()
remember val in ConstantPool at next free slot
add operand to ldr that is MCSymbolRef of Label
On finishParse() callback
Write out all non-empty constant pools
for each Entry in ConstantPool
Emit Entry.Label
Emit Entry.Value
Possible improvements to be added in a later patch:
1. Does not convert load of small constants to mov
(e.g. ldr r0, =0x1 => mov r0, 0x1)
2. Does reuse constant pool entries for same constant
The implementation was tested for ARM, Thumb1, and Thumb2 targets on
linux and darwin.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197708 91177308-0d34-0410-b5e6-96231b3b80d8
18 lines
632 B
ArmAsm
18 lines
632 B
ArmAsm
@RUN: not llvm-mc -triple=armv7-unknown-linux-gnueabi -filetype=obj %s -o %t1 2> %t2
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@RUN: cat %t2 | FileCheck %s
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@RUN: not llvm-mc -triple=armv7-darwin-apple -filetype=obj %s -o %t1_darwin 2> %t2_darwin
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@RUN: cat %t2_darwin | FileCheck %s
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@These tests look for errors that should be reported for invalid object layout
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@with the ldr pseudo. They are tested separately from parse errors because they
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@only trigger when the file has successfully parsed and the object file is about
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@to be written out.
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.text
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foo:
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ldr r0, =0x101
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.space 8000
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@ CHECK: error: out of range pc-relative fixup value
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@ CHECK: ldr r0, =0x101
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@ CHECK: ^
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