[llvm] r241027 - RegisterCoalescer: Cleanup empty subranges after shrinkToUses()

[Matthias Braun]

Author: matze
Date: Mon Jun 29 19:33:44 2015
New Revision: 241027

URL: http://llvm.org/viewvc/llvm-project?rev=241027&view=rev
Log:
RegisterCoalescer: Cleanup empty subranges after shrinkToUses()

A call to removeEmptySubranges() is necessary after every operation that
potentially removes all segments from a subregister range; this case in
the register coalescer was missing.

Added:
    llvm/trunk/test/CodeGen/AMDGPU/subreg-coalescer-undef-use.ll
Modified:
    llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp

Modified: llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp?rev=241027&r1=241026&r2=241027&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp (original)
+++ llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp Mon Jun 29 19:33:44 2015
@@ -1449,6 +1449,7 @@ bool RegisterCoalescer::joinCopy(Machine
                    << format("%04X", S.LaneMask) << ")\n");
       LIS->shrinkToUses(S, LI.reg);
     }
+    LI.removeEmptySubRanges();
   }
   if (ShrinkMainRange) {
     LiveInterval &LI = LIS->getInterval(CP.getDstReg());

Added: llvm/trunk/test/CodeGen/AMDGPU/subreg-coalescer-undef-use.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AMDGPU/subreg-coalescer-undef-use.ll?rev=241027&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/AMDGPU/subreg-coalescer-undef-use.ll (added)
+++ llvm/trunk/test/CodeGen/AMDGPU/subreg-coalescer-undef-use.ll Mon Jun 29 19:33:44 2015
@@ -0,0 +1,20 @@
+; RUN: llc -march=amdgcn -mcpu=SI -o /dev/null %s
+; Don't crash when the use of an undefined value is only detected by the
+; register coalescer because it is hidden with subregister insert/extract.
+target triple="amdgcn--"
+
+define void @foobar(float %a0, float %a1, float addrspace(1)* %out) nounwind {
+entry:
+  %v0 = insertelement <4 x float> undef, float %a0, i32 0
+  br i1 undef, label %ift, label %ife
+
+ift:
+  %v1 = insertelement <4 x float> undef, float %a1, i32 0
+  br label %ife
+
+ife:
+  %val = phi <4 x float> [ %v1, %ift ], [ %v0, %entry ]
+  %v2 = extractelement <4 x float> %val, i32 1
+  store float %v2, float addrspace(1)* %out, align 4
+  ret void
+}