Fix a silly use-after-free issue. A much earlier version of this code

need lots of fanciness around retaining a reference to a Chain's slot in
the BlockToChain map, but that's all gone now. We can just go directly
to allocating the new chain (which will update the mapping for us) and
using it.

Somewhat gross mechanically generated test case replicates the issue
Duncan spotted when actually testing this out.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145120 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/MachineBlockPlacement.cpp b/lib/CodeGen/MachineBlockPlacement.cpp
index 870e24884afbdf40b18ad7fe2717fb0bae484abb..55d804b31e6996ff0a6699e6b32ef8ddb20dd3f9 100644 (file)
--- a/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/lib/CodeGen/MachineBlockPlacement.cpp
@@ -640,8 +640,8 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) {
   SmallVector<MachineOperand, 4> Cond; // For AnalyzeBranch.
   for (MachineFunction::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) {
     MachineBasicBlock *BB = FI;
-    BlockChain *&Chain = BlockToChain[BB];
-    Chain = new (ChainAllocator.Allocate()) BlockChain(BlockToChain, BB);
+    BlockChain *Chain
+      = new (ChainAllocator.Allocate()) BlockChain(BlockToChain, BB);
     // Also, merge any blocks which we cannot reason about and must preserve
     // the exact fallthrough behavior for.
     for (;;) {

diff --git a/test/CodeGen/X86/block-placement.ll b/test/CodeGen/X86/block-placement.ll
index a6ddc4d68eebb8832662c17253f6730096719164..f87d1a6daf7f6e416d945ebae7d7a47e28e87188 100644 (file)
--- a/test/CodeGen/X86/block-placement.ll
+++ b/test/CodeGen/X86/block-placement.ll
@@ -649,3 +649,214 @@ exit:
   ret void
 }
 
+define void @many_unanalyzable_branches() {
+; Ensure that we don't crash as we're building up many unanalyzable branches,
+; blocks, and loops.
+;
+; CHECK: many_unanalyzable_branches
+; CHECK: %entry
+; CHECK: %exit
+
+entry:
+  br label %0
+
+  %val0 = volatile load float* undef
+  %cmp0 = fcmp une float %val0, undef
+  br i1 %cmp0, label %1, label %0
+  %val1 = volatile load float* undef
+  %cmp1 = fcmp une float %val1, undef
+  br i1 %cmp1, label %2, label %1
+  %val2 = volatile load float* undef
+  %cmp2 = fcmp une float %val2, undef
+  br i1 %cmp2, label %3, label %2
+  %val3 = volatile load float* undef
+  %cmp3 = fcmp une float %val3, undef
+  br i1 %cmp3, label %4, label %3
+  %val4 = volatile load float* undef
+  %cmp4 = fcmp une float %val4, undef
+  br i1 %cmp4, label %5, label %4
+  %val5 = volatile load float* undef
+  %cmp5 = fcmp une float %val5, undef
+  br i1 %cmp5, label %6, label %5
+  %val6 = volatile load float* undef
+  %cmp6 = fcmp une float %val6, undef
+  br i1 %cmp6, label %7, label %6
+  %val7 = volatile load float* undef
+  %cmp7 = fcmp une float %val7, undef
+  br i1 %cmp7, label %8, label %7
+  %val8 = volatile load float* undef
+  %cmp8 = fcmp une float %val8, undef
+  br i1 %cmp8, label %9, label %8
+  %val9 = volatile load float* undef
+  %cmp9 = fcmp une float %val9, undef
+  br i1 %cmp9, label %10, label %9
+  %val10 = volatile load float* undef
+  %cmp10 = fcmp une float %val10, undef
+  br i1 %cmp10, label %11, label %10
+  %val11 = volatile load float* undef
+  %cmp11 = fcmp une float %val11, undef
+  br i1 %cmp11, label %12, label %11
+  %val12 = volatile load float* undef
+  %cmp12 = fcmp une float %val12, undef
+  br i1 %cmp12, label %13, label %12
+  %val13 = volatile load float* undef
+  %cmp13 = fcmp une float %val13, undef
+  br i1 %cmp13, label %14, label %13
+  %val14 = volatile load float* undef
+  %cmp14 = fcmp une float %val14, undef
+  br i1 %cmp14, label %15, label %14
+  %val15 = volatile load float* undef
+  %cmp15 = fcmp une float %val15, undef
+  br i1 %cmp15, label %16, label %15
+  %val16 = volatile load float* undef
+  %cmp16 = fcmp une float %val16, undef
+  br i1 %cmp16, label %17, label %16
+  %val17 = volatile load float* undef
+  %cmp17 = fcmp une float %val17, undef
+  br i1 %cmp17, label %18, label %17
+  %val18 = volatile load float* undef
+  %cmp18 = fcmp une float %val18, undef
+  br i1 %cmp18, label %19, label %18
+  %val19 = volatile load float* undef
+  %cmp19 = fcmp une float %val19, undef
+  br i1 %cmp19, label %20, label %19
+  %val20 = volatile load float* undef
+  %cmp20 = fcmp une float %val20, undef
+  br i1 %cmp20, label %21, label %20
+  %val21 = volatile load float* undef
+  %cmp21 = fcmp une float %val21, undef
+  br i1 %cmp21, label %22, label %21
+  %val22 = volatile load float* undef
+  %cmp22 = fcmp une float %val22, undef
+  br i1 %cmp22, label %23, label %22
+  %val23 = volatile load float* undef
+  %cmp23 = fcmp une float %val23, undef
+  br i1 %cmp23, label %24, label %23
+  %val24 = volatile load float* undef
+  %cmp24 = fcmp une float %val24, undef
+  br i1 %cmp24, label %25, label %24
+  %val25 = volatile load float* undef
+  %cmp25 = fcmp une float %val25, undef
+  br i1 %cmp25, label %26, label %25
+  %val26 = volatile load float* undef
+  %cmp26 = fcmp une float %val26, undef
+  br i1 %cmp26, label %27, label %26
+  %val27 = volatile load float* undef
+  %cmp27 = fcmp une float %val27, undef
+  br i1 %cmp27, label %28, label %27
+  %val28 = volatile load float* undef
+  %cmp28 = fcmp une float %val28, undef
+  br i1 %cmp28, label %29, label %28
+  %val29 = volatile load float* undef
+  %cmp29 = fcmp une float %val29, undef
+  br i1 %cmp29, label %30, label %29
+  %val30 = volatile load float* undef
+  %cmp30 = fcmp une float %val30, undef
+  br i1 %cmp30, label %31, label %30
+  %val31 = volatile load float* undef
+  %cmp31 = fcmp une float %val31, undef
+  br i1 %cmp31, label %32, label %31
+  %val32 = volatile load float* undef
+  %cmp32 = fcmp une float %val32, undef
+  br i1 %cmp32, label %33, label %32
+  %val33 = volatile load float* undef
+  %cmp33 = fcmp une float %val33, undef
+  br i1 %cmp33, label %34, label %33
+  %val34 = volatile load float* undef
+  %cmp34 = fcmp une float %val34, undef
+  br i1 %cmp34, label %35, label %34
+  %val35 = volatile load float* undef
+  %cmp35 = fcmp une float %val35, undef
+  br i1 %cmp35, label %36, label %35
+  %val36 = volatile load float* undef
+  %cmp36 = fcmp une float %val36, undef
+  br i1 %cmp36, label %37, label %36
+  %val37 = volatile load float* undef
+  %cmp37 = fcmp une float %val37, undef
+  br i1 %cmp37, label %38, label %37
+  %val38 = volatile load float* undef
+  %cmp38 = fcmp une float %val38, undef
+  br i1 %cmp38, label %39, label %38
+  %val39 = volatile load float* undef
+  %cmp39 = fcmp une float %val39, undef
+  br i1 %cmp39, label %40, label %39
+  %val40 = volatile load float* undef
+  %cmp40 = fcmp une float %val40, undef
+  br i1 %cmp40, label %41, label %40
+  %val41 = volatile load float* undef
+  %cmp41 = fcmp une float %val41, undef
+  br i1 %cmp41, label %42, label %41
+  %val42 = volatile load float* undef
+  %cmp42 = fcmp une float %val42, undef
+  br i1 %cmp42, label %43, label %42
+  %val43 = volatile load float* undef
+  %cmp43 = fcmp une float %val43, undef
+  br i1 %cmp43, label %44, label %43
+  %val44 = volatile load float* undef
+  %cmp44 = fcmp une float %val44, undef
+  br i1 %cmp44, label %45, label %44
+  %val45 = volatile load float* undef
+  %cmp45 = fcmp une float %val45, undef
+  br i1 %cmp45, label %46, label %45
+  %val46 = volatile load float* undef
+  %cmp46 = fcmp une float %val46, undef
+  br i1 %cmp46, label %47, label %46
+  %val47 = volatile load float* undef
+  %cmp47 = fcmp une float %val47, undef
+  br i1 %cmp47, label %48, label %47
+  %val48 = volatile load float* undef
+  %cmp48 = fcmp une float %val48, undef
+  br i1 %cmp48, label %49, label %48
+  %val49 = volatile load float* undef
+  %cmp49 = fcmp une float %val49, undef
+  br i1 %cmp49, label %50, label %49
+  %val50 = volatile load float* undef
+  %cmp50 = fcmp une float %val50, undef
+  br i1 %cmp50, label %51, label %50
+  %val51 = volatile load float* undef
+  %cmp51 = fcmp une float %val51, undef
+  br i1 %cmp51, label %52, label %51
+  %val52 = volatile load float* undef
+  %cmp52 = fcmp une float %val52, undef
+  br i1 %cmp52, label %53, label %52
+  %val53 = volatile load float* undef
+  %cmp53 = fcmp une float %val53, undef
+  br i1 %cmp53, label %54, label %53
+  %val54 = volatile load float* undef
+  %cmp54 = fcmp une float %val54, undef
+  br i1 %cmp54, label %55, label %54
+  %val55 = volatile load float* undef
+  %cmp55 = fcmp une float %val55, undef
+  br i1 %cmp55, label %56, label %55
+  %val56 = volatile load float* undef
+  %cmp56 = fcmp une float %val56, undef
+  br i1 %cmp56, label %57, label %56
+  %val57 = volatile load float* undef
+  %cmp57 = fcmp une float %val57, undef
+  br i1 %cmp57, label %58, label %57
+  %val58 = volatile load float* undef
+  %cmp58 = fcmp une float %val58, undef
+  br i1 %cmp58, label %59, label %58
+  %val59 = volatile load float* undef
+  %cmp59 = fcmp une float %val59, undef
+  br i1 %cmp59, label %60, label %59
+  %val60 = volatile load float* undef
+  %cmp60 = fcmp une float %val60, undef
+  br i1 %cmp60, label %61, label %60
+  %val61 = volatile load float* undef
+  %cmp61 = fcmp une float %val61, undef
+  br i1 %cmp61, label %62, label %61
+  %val62 = volatile load float* undef
+  %cmp62 = fcmp une float %val62, undef
+  br i1 %cmp62, label %63, label %62
+  %val63 = volatile load float* undef
+  %cmp63 = fcmp une float %val63, undef
+  br i1 %cmp63, label %64, label %63
+  %val64 = volatile load float* undef
+  %cmp64 = fcmp une float %val64, undef
+  br i1 %cmp64, label %65, label %64
+
+  br label %exit
+exit:
+  ret void
+}