[LiveIntervals] Handle moving up dead partial write

Summary:
In the test case, the machine scheduler moves a dead write to a subreg
up into the middle of a segment of the overall reg's live range, where
the segment had liveness only for other subregs in the reg.
handleMoveUp created an invalid live range, causing an assert a bit
later.

This commit fixes it to handle that situation. The segment is split in
two at the insertion point, and the part after the split, and any
subsequent segments up to the old position, are changed to be defined by
the moved def.

V2: Better test.

Subscribers: MatzeB, nhaehnle, llvm-commits

Differential Revision: https://reviews.llvm.org/D43478

Change-Id: Ibc42445ddca84e79ad1f616401015d22bc63832e
llvm-svn: 326087

1 files changed, 25 insertions, 0 deletions

diff --git a/llvm/unittests/MI/LiveIntervalTest.cpp b/llvm/unittests/MI/LiveIntervalTest.cpp
index d614c7f..a39fd7f 100644
--- a/llvm/unittests/MI/LiveIntervalTest.cpp
+++ b/llvm/unittests/MI/LiveIntervalTest.cpp
@@ -395,6 +395,31 @@ TEST(LiveIntervalTest, SubRegMoveUp) {
   });
 }
 
+TEST(LiveIntervalTest, DeadSubRegMoveUp) {
+  // handleMoveUp had a bug where moving a dead subreg def into the middle of
+  // an earlier segment resulted in an invalid live range.
+  liveIntervalTest(R"MIR(
+    undef %125.sub0:vreg_128 = V_MOV_B32_e32 0, implicit $exec
+    %125.sub1:vreg_128 = COPY %125.sub0
+    %125.sub2:vreg_128 = COPY %125.sub0
+    undef %51.sub0:vreg_128 = V_MOV_B32_e32 898625526, implicit $exec
+    %51.sub1:vreg_128 = COPY %51.sub0
+    %51.sub2:vreg_128 = COPY %51.sub0
+    %52:vgpr_32 = V_MOV_B32_e32 986714345, implicit $exec
+    %54:vgpr_32 = V_MOV_B32_e32 1742342378, implicit $exec
+    %57:vgpr_32 = V_MOV_B32_e32 3168768712, implicit $exec
+    %59:vgpr_32 = V_MOV_B32_e32 1039972644, implicit $exec
+    %60:vgpr_32 = V_MAD_F32 0, %52, 0, undef %61:vgpr_32, 0, %59, 0, 0, implicit $exec
+    %63:vgpr_32 = V_ADD_F32_e32 %51.sub3, undef %64:vgpr_32, implicit $exec
+    dead %66:vgpr_32 = V_MAD_F32 0, %60, 0, undef %67:vgpr_32, 0, %125.sub2, 0, 0, implicit $exec
+    undef %124.sub1:vreg_128 = V_MAD_F32 0, %57, 0, undef %70:vgpr_32, 0, %125.sub1, 0, 0, implicit $exec
+    %124.sub0:vreg_128 = V_MAD_F32 0, %54, 0, undef %73:vgpr_32, 0, %125.sub0, 0, 0, implicit $exec
+    dead undef %125.sub3:vreg_128 = V_MAC_F32_e32 %63, undef %76:vgpr_32, %125.sub3, implicit $exec
+)MIR", [](MachineFunction &MF, LiveIntervals &LIS) {
+    testHandleMove(MF, LIS, 15, 12);
+  });
+}
+
 int main(int argc, char **argv) {
   ::testing::InitGoogleTest(&argc, argv);
   initLLVM();