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Add a new function attribute, 'alignstack'. It will indicate (when the backends

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implement support for it) that the stack should be forcibly realigned in the
prologue (and the process reversed in the epilogue).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95945 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Charles Davis
2010-02-12 00:31:15 +00:00
parent 4a540f0593
commit 1e063d14df
6 changed files with 71 additions and 1 deletions
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29
include/llvm/Attributes.h
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@@ -60,6 +60,11 @@ const Attributes NoImplicitFloat = 1<<23; /// disable implicit floating point
const Attributes Naked = 1<<24; ///< Naked function
const Attributes InlineHint = 1<<25; ///< source said inlining was
///desirable
const Attributes StackAlignment = 31<<26; ///< Alignment of stack for
///function (5 bits) stored as log2
///of alignment with +1 bias
///0 means unaligned (different from
///alignstack(1))
/// @brief Attributes that only apply to function parameters.
const Attributes ParameterOnly = ByVal | Nest | StructRet | NoCapture;
@@ -68,7 +73,7 @@ const Attributes ParameterOnly = ByVal | Nest | StructRet | NoCapture;
/// be used on return values or function parameters.
const Attributes FunctionOnly = NoReturn | NoUnwind | ReadNone | ReadOnly |
NoInline | AlwaysInline | OptimizeForSize | StackProtect | StackProtectReq |
NoRedZone | NoImplicitFloat | Naked | InlineHint;
NoRedZone | NoImplicitFloat | Naked | InlineHint | StackAlignment;
/// @brief Parameter attributes that do not apply to vararg call arguments.
const Attributes VarArgsIncompatible = StructRet;
@@ -105,6 +110,28 @@ inline unsigned getAlignmentFromAttrs(Attributes A) {
return 1U << ((Align >> 16) - 1);
}
/// This turns an int stack alignment (which must be a power of 2) into
/// the form used internally in Attributes.
inline Attributes constructStackAlignmentFromInt(unsigned i) {
// Default alignment, allow the target to define how to align it.
if (i == 0)
return 0;
assert(isPowerOf2_32(i) && "Alignment must be a power of two.");
assert(i <= 0x40000000 && "Alignment too large.");
return (Log2_32(i)+1) << 26;
}
/// This returns the stack alignment field of an attribute as a byte alignment
/// value.
inline unsigned getStackAlignmentFromAttrs(Attributes A) {
Attributes StackAlign = A & Attribute::StackAlignment;
if (StackAlign == 0)
return 0;
return 1U << ((StackAlign >> 26) - 1);
}
/// The set of Attributes set in Attributes is converted to a
/// string of equivalent mnemonics. This is, presumably, for writing out