[llvm] r223727 - Handle early-clobber registers in the aggressive anti-dep breaker

[Hal Finkel]

Author: hfinkel
Date: Mon Dec  8 19:00:59 2014
New Revision: 223727

URL: http://llvm.org/viewvc/llvm-project?rev=223727&view=rev
Log:
Handle early-clobber registers in the aggressive anti-dep breaker

The aggressive anti-dep breaker, used by the PowerPC backend during post-RA
scheduling (but is available to all targets), did not handle early-clobber MI
operands (at all). When constructing the list of available registers for the
replacement of some def operand, check the using instructions, and remove
registers assigned to early-clobbered defs from the set.

Fixes PR21452.

Added:
    llvm/trunk/test/CodeGen/PowerPC/post-ra-ec.ll
Modified:
    llvm/trunk/lib/CodeGen/AggressiveAntiDepBreaker.cpp

Modified: llvm/trunk/lib/CodeGen/AggressiveAntiDepBreaker.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AggressiveAntiDepBreaker.cpp?rev=223727&r1=223726&r2=223727&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AggressiveAntiDepBreaker.cpp (original)
+++ llvm/trunk/lib/CodeGen/AggressiveAntiDepBreaker.cpp Mon Dec  8 19:00:59 2014
@@ -673,6 +673,21 @@ bool AggressiveAntiDepBreaker::FindSuita
           goto next_super_reg;
       }
 
+      // We cannot rename 'Reg' to 'NewReg' if one of the uses of 'Reg' also
+      // defines 'NewReg' via an early-clobber operand.
+      auto Range = RegRefs.equal_range(Reg);
+      for (auto Q = Range.first, QE = Range.second; Q != QE; ++Q) {
+        auto UseMI = Q->second.Operand->getParent();
+        int Idx = UseMI->findRegisterDefOperandIdx(NewReg, false, true, TRI);
+        if (Idx == -1)
+          continue;
+
+        if (UseMI->getOperand(Idx).isEarlyClobber()) {
+          DEBUG(dbgs() << "(ec)");
+          goto next_super_reg;
+        }
+      }
+
       // Record that 'Reg' can be renamed to 'NewReg'.
       RenameMap.insert(std::pair<unsigned, unsigned>(Reg, NewReg));
     }

Added: llvm/trunk/test/CodeGen/PowerPC/post-ra-ec.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/post-ra-ec.ll?rev=223727&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/post-ra-ec.ll (added)
+++ llvm/trunk/test/CodeGen/PowerPC/post-ra-ec.ll Mon Dec  8 19:00:59 2014
@@ -0,0 +1,47 @@
+; RUN: llc -mcpu=pwr7 < %s | FileCheck %s
+target datalayout = "E-m:e-i64:64-n32:64"
+target triple = "powerpc64-unknown-linux-gnu"
+
+%struct.inode.0.12.120 = type { i8* }
+%struct.kstat2.1.13.121 = type { i32 }
+%struct.task_struct.4.16.124 = type { i8*, %struct.atomic_t.2.14.122, %struct.signal_struct.3.15.123* }
+%struct.atomic_t.2.14.122 = type { i32 }
+%struct.signal_struct.3.15.123 = type { i64 }
+%struct.pid.5.17.125 = type { i8* }
+
+; Function Attrs: nounwind
+define signext i32 @proc_task_getattr(%struct.inode.0.12.120* nocapture readonly %inode, %struct.kstat2.1.13.121* nocapture %stat) #0 {
+entry:
+  %call1.i = tail call %struct.task_struct.4.16.124* @get_pid_task(%struct.pid.5.17.125* undef, i32 zeroext 0) #0
+  br i1 undef, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  %0 = load i64* undef, align 8
+  %conv.i = trunc i64 %0 to i32
+  %1 = load i32* null, align 4
+  %add = add i32 %1, %conv.i
+  store i32 %add, i32* null, align 4
+  %counter.i.i = getelementptr inbounds %struct.task_struct.4.16.124* %call1.i, i64 0, i32 1, i32 0
+  %2 = tail call i32 asm sideeffect "\09lwsync\0A1:\09lwarx\09$0,0,$1\09\09# atomic_dec_return\0A\09addic\09$0,$0,-1\0A\09stwcx.\09$0,0,$1\0A\09bne-\091b\0A\09sync\0A", "=&r,r,~{cr0},~{xer},~{memory}"(i32* %counter.i.i) #0
+  %cmp.i = icmp eq i32 %2, 0
+  br i1 %cmp.i, label %if.then.i, label %if.end
+
+; CHECK-LABEL: @proc_task_getattr
+; CHECK-NOT: stwcx. [[REG:[0-9]+]],0,[[REG]]
+; CHECK: blr
+
+if.then.i:                                        ; preds = %if.then
+  %3 = bitcast %struct.task_struct.4.16.124* %call1.i to i8*
+  tail call void @foo(i8* %3) #0
+  unreachable
+
+if.end:                                           ; preds = %if.then, %entry
+  ret i32 0
+}
+
+declare void @foo(i8*)
+
+declare %struct.task_struct.4.16.124* @get_pid_task(%struct.pid.5.17.125*, i32 zeroext)
+
+attributes #0 = { nounwind }
+