[llvm] r303396 - LiveIntervalAnalysis: Fix missing case in pruneSubRegValues()

[Matthias Braun via llvm-commits]

Author: matze
Date: Thu May 18 19:18:03 2017
New Revision: 303396

URL: http://llvm.org/viewvc/llvm-project?rev=303396&view=rev
Log:
LiveIntervalAnalysis: Fix missing case in pruneSubRegValues()

pruneSubRegValues() needs to remove subregister ranges starting at
instructions that later get removed by eraseInstrs(). It missed to check
one case in which eraseInstrs() would remove an instruction.

Fixes http://llvm.org/PR32688

Added:
    llvm/trunk/test/CodeGen/AMDGPU/regcoalesce-prune.mir
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=303396&r1=303395&r2=303396&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp (original)
+++ llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp Thu May 18 19:18:03 2017
@@ -2666,11 +2666,17 @@ void JoinVals::pruneSubRegValues(LiveInt
   // Look for values being erased.
   bool DidPrune = false;
   for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
-    if (Vals[i].Resolution != CR_Erase)
+    // We should trigger in all cases in which eraseInstrs() does something.
+    // match what eraseInstrs() is doing, print a message so
+    if (Vals[i].Resolution != CR_Erase &&
+        (Vals[i].Resolution != CR_Keep || !Vals[i].ErasableImplicitDef ||
+         !Vals[i].Pruned))
       continue;
 
     // Check subranges at the point where the copy will be removed.
     SlotIndex Def = LR.getValNumInfo(i)->def;
+    // Print message so mismatches with eraseInstrs() can be diagnosed.
+    DEBUG(dbgs() << "\t\tExpecting instruction removal at " << Def << '\n');
     for (LiveInterval::SubRange &S : LI.subranges()) {
       LiveQueryResult Q = S.Query(Def);
 

Added: llvm/trunk/test/CodeGen/AMDGPU/regcoalesce-prune.mir
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AMDGPU/regcoalesce-prune.mir?rev=303396&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/AMDGPU/regcoalesce-prune.mir (added)
+++ llvm/trunk/test/CodeGen/AMDGPU/regcoalesce-prune.mir Thu May 18 19:18:03 2017
@@ -0,0 +1,31 @@
+# RUN: llc -o - %s -mtriple=amdgcn-amd-amdhsa-opencl -run-pass=simple-register-coalescing | FileCheck %s
+---
+# Checks for a bug where subregister liveranges were not properly pruned for
+# an IMPLCITI_DEF that gets removed completely.
+#
+# CHECK-LABEL: name: func
+# IMPLICIT_DEF should be gone without llc hitting assertion failures.
+# CHECK-NOT: IMPLCITI_DEF
+name: func
+tracksRegLiveness: true
+body: |
+  bb.0:
+    undef %5.sub1 = V_MOV_B32_e32 0, implicit %exec
+    %6 = COPY %5
+    S_CBRANCH_VCCZ %bb.2, implicit undef %vcc
+
+  bb.1:
+    %1 : sreg_32_xm0 = S_MOV_B32 0
+    undef %0.sub0 : sreg_64 = COPY %1
+    %0.sub1 = COPY %1
+    %4 : vreg_64 = COPY killed %0
+    %5 : vreg_64 = IMPLICIT_DEF
+    %6 : vreg_64 = COPY killed %4
+
+  bb.2:
+    %2 : vgpr_32 = V_CVT_F32_I32_e32 killed %5.sub1, implicit %exec
+
+  bb.3:
+    %3 : vgpr_32 = V_CVT_F32_I32_e32 killed %6.sub1, implicit %exec
+    S_ENDPGM
+...