[BDCE] Don't forget uses of root instructions seen before the instruction itself

When visiting the initial list of "root" instructions (those which must always
be alive), for those that are integer-valued (such as invokes returning an
integer), we mark their bits as (initially) all dead (we might, obviously, find
uses of those bits later, but all bits are assumed dead until proven
otherwise). Don't do so, however, if we're already seen a use of those bits by
another root instruction (such as a store).

Fixes a miscompile of the sanitizer unit tests on x86_64.

Also, add a debug line for visiting the root instructions, and remove a debug
line which tried to print instructions being removed (printing dead
instructions is dangerous, and can sometimes crash).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229618 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/BDCE.cpp b/lib/Transforms/Scalar/BDCE.cpp
index afe0cd13e2296ce5fd7ac382b95ac16916c4b58d..e5a7ad6388d8d7aecb3e77c95651b784ce6321f6 100644 (file)
--- a/lib/Transforms/Scalar/BDCE.cpp
+++ b/lib/Transforms/Scalar/BDCE.cpp
@@ -277,13 +277,17 @@ bool BDCE::runOnFunction(Function& F) {
     if (!isAlwaysLive(&I))
       continue;
 
+    DEBUG(dbgs() << "BDCE: Root: " << I);
     // For integer-valued instructions, set up an initial empty set of alive
     // bits and add the instruction to the work list. For other instructions
     // add their operands to the work list (for integer values operands, mark
     // all bits as live).
     if (IntegerType *IT = dyn_cast<IntegerType>(I.getType())) {
-      AliveBits[&I] = APInt(IT->getBitWidth(), 0);
-      Worklist.push_back(&I);
+      if (!AliveBits.count(&I)) {
+        AliveBits[&I] = APInt(IT->getBitWidth(), 0);
+        Worklist.push_back(&I);
+      }
+
       continue;
     }
 
@@ -388,7 +392,6 @@ bool BDCE::runOnFunction(Function& F) {
     if (isAlwaysLive(&I))
       continue;
 
-    DEBUG(dbgs() << "BDCE: Removing: " << I << " (unused)\n");
     Worklist.push_back(&I);
     I.dropAllReferences();
     Changed = true;

diff --git a/test/Transforms/BDCE/order.ll b/test/Transforms/BDCE/order.ll
new file mode 100644 (file)
index 0000000..301f447
--- /dev/null
+++ b/test/Transforms/BDCE/order.ll
@@ -0,0 +1,37 @@
+; RUN: opt -bdce -S < %s | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare i32 @__gxx_personality_v0(...)
+
+define fastcc void @_ZN11__sanitizerL12TestRegistryEPNS_14ThreadRegistryEb() #0 {
+entry:
+  br i1 undef, label %if.else, label %entry.if.end_crit_edge
+
+if.else:
+  ret void
+
+invoke.cont70:
+  store i32 %call71, i32* undef, align 4
+  br label %if.else
+
+; CHECK-LABEL: @_ZN11__sanitizerL12TestRegistryEPNS_14ThreadRegistryEb
+; CHECK: store i32 %call71
+
+lpad65.loopexit.split-lp.loopexit.split-lp:
+  br label %if.else
+
+lpad65.loopexit.split-lp.loopexit.split-lp.loopexit:
+  %lpad.loopexit1121 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  br label %lpad65.loopexit.split-lp.loopexit.split-lp
+
+entry.if.end_crit_edge:
+  %call71 = invoke i32 @_ZN11__sanitizer14ThreadRegistry12CreateThreadEmbjPv()
+          to label %invoke.cont70 unwind label %lpad65.loopexit.split-lp.loopexit.split-lp.loopexit
+}
+
+declare i32 @_ZN11__sanitizer14ThreadRegistry12CreateThreadEmbjPv()
+
+attributes #0 = { uwtable }
+