maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[RegisterClassInfo] Return non-zero for RC without allocatable reg 

In some case, the RC may have 0 allocatable reg.
eg: VRSAVERC in PowerPC, which has only 1 reg, but it is also reserved.

The curreent implementation will keep calling the computePSetLimit because
getRegPressureSetLimit assume computePSetLimit will return a non-zero value.

The fix simply early return the value from TableGen for such special case.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D92907
This commit is contained in:
Jinsong Ji 2021-01-05 15:37:16 +00:00
parent 51d5991f04
commit f26bc0ddd5
2 changed files with 11 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
llvm/lib/CodeGen/RegisterClassInfo.cpp
View File

@ -188,7 +188,14 @@ unsigned RegisterClassInfo::computePSetLimit(unsigned Idx) const {
}
assert(RC && "Failed to find register class");
compute(RC);
unsigned NReserved = RC->getNumRegs() - getNumAllocatableRegs(RC);
return TRI->getRegPressureSetLimit(*MF, Idx) -
TRI->getRegClassWeight(RC).RegWeight * NReserved;
unsigned NAllocatableRegs = getNumAllocatableRegs(RC);
unsigned RegPressureSetLimit = TRI->getRegPressureSetLimit(*MF, Idx);
// If all the regs are reserved, return raw RegPressureSetLimit.
// One example is VRSAVERC in PowerPC.
// Avoid returning zero, getRegPressureSetLimit(Idx) assumes computePSetLimit
// return non-zero value.
if (NAllocatableRegs == 0)
return RegPressureSetLimit;
unsigned NReserved = RC->getNumRegs() - NAllocatableRegs;
return RegPressureSetLimit - TRI->getRegClassWeight(RC).RegWeight * NReserved;
}

2
llvm/test/CodeGen/PowerPC/compute-regpressure.ll
View File

@ -1,7 +1,7 @@
; REQUIRES: asserts
; RUN: llc -debug-only=regalloc < %s 2>&1 |FileCheck %s --check-prefix=DEBUG
; DEBUG-COUNT-3: AllocationOrder(VRSAVERC) = [ ]
; DEBUG-COUNT-1: AllocationOrder(VRSAVERC) = [ ]
target triple = "powerpc64le-unknown-linux-gnu"