[PATCH] D17087: [RegAlloc] CalcSpillWeights: Fix infinite loop

[Tim Shen via llvm-commits]

timshen updated this revision to Diff 47550.
timshen added a comment.

Attached reduced test case.

Sorry, I also found that this change is wrong. I thought it works but I forgot to turn on assertion. This test case triggers an assertion failure with this change. I will do more investigation.


http://reviews.llvm.org/D17087

Files:
  lib/CodeGen/CalcSpillWeights.cpp
  test/CodeGen/PowerPC/calc-spill-weight-circle.ll

Index: test/CodeGen/PowerPC/calc-spill-weight-circle.ll
===================================================================
--- /dev/null
+++ test/CodeGen/PowerPC/calc-spill-weight-circle.ll
@@ -0,0 +1,48 @@
+; RUN: llc < %s | FileCheck %s
+; CHECK-LABEL: TestFoo
+target triple = "powerpc64le-unknown-linux-gnu"
+
+declare double @sqrt(double)
+
+declare double @cos(double)
+
+declare <2 x double> @llvm.fma.v2f64(<2 x double>, <2 x double>, <2 x double>)
+
+define void @TestFoo() {
+bb3:
+  %tmp = load <2 x double>, <2 x double>* undef
+  %tmp4 = fsub <2 x double> zeroinitializer, undef
+  %tmp5 = fsub <2 x double> zeroinitializer, undef
+  %tmp6 = call <2 x double> @llvm.fma.v2f64(<2 x double> undef, <2 x double> undef, <2 x double> %tmp)
+  %tmp7 = fsub <2 x double> %tmp4, %tmp6
+  %tmp8 = call <2 x double> @llvm.fma.v2f64(<2 x double> %tmp7, <2 x double> undef, <2 x double> %tmp)
+  %tmp9 = call <2 x double> @llvm.fma.v2f64(<2 x double> undef, <2 x double> undef, <2 x double> %tmp)
+  %tmp10 = fsub <2 x double> %tmp5, %tmp9
+  %tmp11 = call <2 x double> @llvm.fma.v2f64(<2 x double> %tmp10, <2 x double> undef, <2 x double> %tmp)
+  %tmp12 = load <2 x double>, <2 x double>* undef
+  %tmp13 = call <2 x double> @llvm.fma.v2f64(<2 x double> undef, <2 x double> zeroinitializer, <2 x double> %tmp12)
+  br i1 undef, label %bb23, label %bb24
+
+bb15:
+  %tmp16 = call double @cos(double undef)
+  %tmp17 = call <2 x double> @llvm.fma.v2f64(<2 x double> %tmp11, <2 x double> undef, <2 x double> undef)
+  %tmp18 = fadd <2 x double> %tmp17, undef
+  %tmp19 = fsub <2 x double> %tmp18, undef
+  %tmp20 = call <2 x double> @llvm.fma.v2f64(<2 x double> %tmp19, <2 x double> undef, <2 x double> undef)
+  store <2 x double> %tmp20, <2 x double>* undef
+  %tmp21 = fsub <2 x double> %tmp13, undef
+  %tmp22 = call <2 x double> @llvm.fma.v2f64(<2 x double> %tmp21, <2 x double> undef, <2 x double> undef)
+  store <2 x double> %tmp22, <2 x double>* undef
+  ret void
+
+bb23:
+  %exitcond.i.i.i16.i = icmp eq i32 undef, 10
+  br i1 %exitcond.i.i.i16.i, label %bb15, label %bb23
+
+bb24:
+  %tmp25 = call double @sqrt(double undef)
+  %tmp26 = fsub <2 x double> %tmp8, undef
+  %tmp27 = call <2 x double> @llvm.fma.v2f64(<2 x double> %tmp26, <2 x double> undef, <2 x double> undef)
+  store <2 x double> %tmp27, <2 x double>* undef
+  ret void
+}
Index: lib/CodeGen/CalcSpillWeights.cpp
===================================================================
--- lib/CodeGen/CalcSpillWeights.cpp
+++ lib/CodeGen/CalcSpillWeights.cpp
@@ -74,12 +74,12 @@
 }
 
 // Check if all values in LI are rematerializable
-static bool isRematerializable(const LiveInterval &LI,
-                               const LiveIntervals &LIS,
-                               VirtRegMap *VRM,
+static bool isRematerializable(const LiveInterval &LI, const LiveIntervals &LIS,
+                               const VirtRegMap *VRM,
                                const TargetInstrInfo &TII) {
   unsigned Reg = LI.reg;
   unsigned Original = VRM ? VRM->getOriginal(Reg) : 0;
+  SmallPtrSet<const VNInfo *, 4> Visited;
   for (LiveInterval::const_vni_iterator I = LI.vni_begin(), E = LI.vni_end();
        I != E; ++I) {
     const VNInfo *VNI = *I;
@@ -113,6 +113,8 @@
         const LiveInterval &SrcLI = LIS.getInterval(Reg);
         LiveQueryResult SrcQ = SrcLI.Query(VNI->def);
         VNI = SrcQ.valueIn();
+        if (!Visited.insert(VNI).second)
+          break;
         assert(VNI && "Copy from non-existing value");
         if (VNI->isPHIDef())
           return false;


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