Gabe Black has submitted this change. (
https://gem5-review.googlesource.com/c/public/gem5/+/36876 )
Change subject: cpu: Access src and dest reg indexes using a pointer to
member.
......................................................................
cpu: Access src and dest reg indexes using a pointer to member.
This will eventually let subclasses provide their own appropriately
sized storage for these indexes. By using a pointer to member instead of
a regular pointer, we ensure that even if the StaticInst is copied/moved
somewhere, it will still find its indexes correctly, without any
additional performance overhead or maintenance.
Unfortunately C++ has decided that arrays with known bounds are not
convertible/compatible with arrays with unknown bounds. I've found at
least two standards proposals in various stages of acceptance which say
that that's dumb and they should change that (because it's dumb and they
should change that), but in the mean time we can get everything to
compile by using the reinterpret_cast hammer. While this is
*technically* undefined behavior, it's basically not and should be
pretty safe.
Change-Id: Id747b0cf68d1a0b4809ebb66a32472187110d7d8
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/36876
Maintainer: Gabe Black <[email protected]>
Tested-by: kokoro <[email protected]>
Reviewed-by: Giacomo Travaglini <[email protected]>
---
M src/cpu/static_inst.hh
1 file changed, 28 insertions(+), 10 deletions(-)
Approvals:
Giacomo Travaglini: Looks good to me, approved
Gabe Black: Looks good to me, approved
kokoro: Regressions pass
diff --git a/src/cpu/static_inst.hh b/src/cpu/static_inst.hh
index 4f3dd04..22e55ca 100644
--- a/src/cpu/static_inst.hh
+++ b/src/cpu/static_inst.hh
@@ -93,11 +93,16 @@
MaxInstDestRegs = TheISA::MaxInstDestRegs //< Max dest regs
};
+ using RegIdArrayPtr = RegId (StaticInst:: *)[];
+
private:
- /// See destRegIdx().
- RegId _destRegIdx[MaxInstDestRegs];
/// See srcRegIdx().
RegId _srcRegIdx[MaxInstSrcRegs];
+ RegIdArrayPtr _srcRegIdxPtr = nullptr;
+
+ /// See destRegIdx().
+ RegId _destRegIdx[MaxInstDestRegs];
+ RegIdArrayPtr _destRegIdxPtr = nullptr;
protected:
@@ -236,15 +241,23 @@
/// Return logical index (architectural reg num) of i'th destination
reg.
/// Only the entries from 0 through numDestRegs()-1 are valid.
- const RegId& destRegIdx(int i) const { return _destRegIdx[i]; }
+ const RegId &destRegIdx(int i) const { return
(this->*_destRegIdxPtr)[i]; }
- void setDestRegIdx(int i, const RegId &val) { _destRegIdx[i] = val; }
+ void
+ setDestRegIdx(int i, const RegId &val)
+ {
+ (this->*_destRegIdxPtr)[i] = val;
+ }
/// Return logical index (architectural reg num) of i'th source reg.
/// Only the entries from 0 through numSrcRegs()-1 are valid.
- const RegId& srcRegIdx(int i) const { return _srcRegIdx[i]; }
+ const RegId &srcRegIdx(int i) const { return
(this->*_srcRegIdxPtr)[i]; }
- void setSrcRegIdx(int i, const RegId &val) { _srcRegIdx[i] = val; }
+ void
+ setSrcRegIdx(int i, const RegId &val)
+ {
+ (this->*_srcRegIdxPtr)[i] = val;
+ }
/// Pointer to a statically allocated "null" instruction object.
static StaticInstPtr nullStaticInstPtr;
@@ -283,10 +296,15 @@
/// the fields that are meaningful for the particular
/// instruction.
StaticInst(const char *_mnemonic, ExtMachInst _machInst, OpClass
__opClass)
- : _opClass(__opClass), _numSrcRegs(0), _numDestRegs(0),
- _numFPDestRegs(0), _numIntDestRegs(0), _numCCDestRegs(0),
- _numVecDestRegs(0), _numVecElemDestRegs(0),
_numVecPredDestRegs(0),
- machInst(_machInst), mnemonic(_mnemonic), cachedDisassembly(0)
+ : _srcRegIdxPtr(
+ reinterpret_cast<RegIdArrayPtr>(&StaticInst::_srcRegIdx)),
+ _destRegIdxPtr(
+ reinterpret_cast<RegIdArrayPtr>(&StaticInst::_destRegIdx)),
+ _opClass(__opClass),
+ _numSrcRegs(0), _numDestRegs(0), _numFPDestRegs(0),
+ _numIntDestRegs(0), _numCCDestRegs(0), _numVecDestRegs(0),
+ _numVecElemDestRegs(0), _numVecPredDestRegs(0),
machInst(_machInst),
+ mnemonic(_mnemonic), cachedDisassembly(0)
{ }
public:
--
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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: Id747b0cf68d1a0b4809ebb66a32472187110d7d8
Gerrit-Change-Number: 36876
Gerrit-PatchSet: 8
Gerrit-Owner: Gabe Black <[email protected]>
Gerrit-Reviewer: Andreas Sandberg <[email protected]>
Gerrit-Reviewer: Daniel Carvalho <[email protected]>
Gerrit-Reviewer: Gabe Black <[email protected]>
Gerrit-Reviewer: Giacomo Travaglini <[email protected]>
Gerrit-Reviewer: kokoro <[email protected]>
Gerrit-MessageType: merged
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