From 05e2245fc6485c6cdd32e45d25082b08ffe27074 Mon Sep 17 00:00:00 2001 From: Jakob Stoklund Olesen Date: Wed, 30 May 2012 21:46:58 +0000 Subject: [PATCH] Prioritize smaller register classes for urgent evictions. It helps compile exotic inline asm. In the test case, normal GR32 virtual registers use up eax-edx so the final GR32_ABCD live range has no registers left. Since all the live ranges were tiny, we had no way of prioritizing the smaller register class. This patch allows tiny unspillable live ranges to be evicted by tiny unspillable live ranges from a smaller register class. llvm-svn: 157715 --- llvm/lib/CodeGen/RegAllocGreedy.cpp | 8 +++++++- llvm/test/CodeGen/X86/inline-asm.ll | 9 +++++++++ 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/llvm/lib/CodeGen/RegAllocGreedy.cpp b/llvm/lib/CodeGen/RegAllocGreedy.cpp index 7808552efcbd..426e0383786d 100644 --- a/llvm/lib/CodeGen/RegAllocGreedy.cpp +++ b/llvm/lib/CodeGen/RegAllocGreedy.cpp @@ -558,7 +558,13 @@ bool RAGreedy::canEvictInterference(LiveInterval &VirtReg, unsigned PhysReg, // Once a live range becomes small enough, it is urgent that we find a // register for it. This is indicated by an infinite spill weight. These // urgent live ranges get to evict almost anything. - bool Urgent = !VirtReg.isSpillable() && Intf->isSpillable(); + // + // Also allow urgent evictions of unspillable ranges from a strictly + // larger allocation order. + bool Urgent = !VirtReg.isSpillable() && + (Intf->isSpillable() || + RegClassInfo.getNumAllocatableRegs(MRI->getRegClass(VirtReg.reg)) < + RegClassInfo.getNumAllocatableRegs(MRI->getRegClass(Intf->reg))); // Only evict older cascades or live ranges without a cascade. unsigned IntfCascade = ExtraRegInfo[Intf->reg].Cascade; if (Cascade <= IntfCascade) { diff --git a/llvm/test/CodeGen/X86/inline-asm.ll b/llvm/test/CodeGen/X86/inline-asm.ll index eef6c2f377a7..e6eb9efd8c78 100644 --- a/llvm/test/CodeGen/X86/inline-asm.ll +++ b/llvm/test/CodeGen/X86/inline-asm.ll @@ -43,3 +43,12 @@ entry: %0 = tail call i8 asm sideeffect "xchg $0, $1", "=r,*m,0,~{memory},~{dirflag},~{fpsr},~{flags}"(i32* %p, i1 %desired) nounwind ret void } + +; +; The constrained GR32_ABCD register class of the 'q' constraint requires +; special handling after the preceding outputs used up eax-edx. +define void @constrain_abcd(i8* %h) nounwind ssp { +entry: + %0 = call { i32, i32, i32, i32, i32 } asm sideeffect "", "=&r,=&r,=&r,=&r,=&q,r,~{ecx},~{memory},~{dirflag},~{fpsr},~{flags}"(i8* %h) nounwind + ret void +}