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[ABI] Rewrite RegisterIsCalleeSaved. 

The goal of this patch is twofold:
First, it removes a wrong comment (at least, not correctly describing
what the function does).
Then, it rewrites the function to use a StringSwitch where the
registers are enumerated explicitly instead of being computed
programmatically. Other than being much shorter, it's much easier to
read (and given the ABI won't change anytime soon, I don't think
there's need to generalize).

While here, I added an assert that the register name is always empty,
as the previous implementation of the function assumed so.

Differential Revision:  https://reviews.llvm.org/D37420

llvm-svn: 312501
This commit is contained in:
Davide Italiano 2017-09-04 21:21:12 +00:00
parent 9e68b734d6
commit cd28bce8df
1 changed files with 11 additions and 46 deletions
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57
lldb/source/Plugins/ABI/SysV-x86_64/ABISysV_x86_64.cpp
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@ -13,6 +13,7 @@
// C++ Includes
// Other libraries and framework includes
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/ADT/Triple.h"
// Project includes
@ -1908,52 +1909,16 @@ bool ABISysV_x86_64::RegisterIsVolatile(const RegisterInfo *reg_info) {
// It's being revised & updated at https://github.com/hjl-tools/x86-psABI/
bool ABISysV_x86_64::RegisterIsCalleeSaved(const RegisterInfo *reg_info) {
if (reg_info) {
// Preserved registers are :
// rbx, rsp, rbp, r12, r13, r14, r15
// mxcsr (partially preserved)
// x87 control word
const char *name = reg_info->name;
if (name[0] == 'r') {
switch (name[1]) {
case '1': // r12, r13, r14, r15
if (name[2] >= '2' && name[2] <= '5')
return name[3] == '\0';
break;
default:
break;
}
}
// Accept shorter-variant versions, rbx/ebx, rip/ eip, etc.
if (name[0] == 'r' || name[0] == 'e') {
switch (name[1]) {
case 'b': // rbp, rbx
if (name[2] == 'p' || name[2] == 'x')
return name[3] == '\0';
break;
case 'i': // rip
if (name[2] == 'p')
return name[3] == '\0';
break;
case 's': // rsp
if (name[2] == 'p')
return name[3] == '\0';
break;
}
}
if (name[0] == 's' && name[1] == 'p' && name[2] == '\0') // sp
return true;
if (name[0] == 'f' && name[1] == 'p' && name[2] == '\0') // fp
return true;
if (name[0] == 'p' && name[1] == 'c' && name[2] == '\0') // pc
return true;
}
return false;
if (!reg_info)
return false;
assert(reg_info->name != nullptr && "unnamed register?");
std::string Name = std::string(reg_info->name);
bool IsCalleeSaved =
llvm::StringSwitch<bool>(Name)
.Cases("r12", "r13", "r14", "r15", "rbp", "ebp", "rbx", "ebx", true)
.Cases("rip", "eip", "rsp", "esp", "sp", "fp", "pc", true)
.Default(false);
return IsCalleeSaved;
}
void ABISysV_x86_64::Initialize() {