[llvm-commits] [llvm] r89658 - in /llvm/trunk: lib/Transforms/Scalar/SCCP.cpp test/Transforms/IPConstantProp/user-with-multiple-uses.ll

[Dan Gohman]

Author: djg
Date: Mon Nov 23 10:13:39 2009
New Revision: 89658

URL: http://llvm.org/viewvc/llvm-project?rev=89658&view=rev
Log:
Fix a use of an invalidated iterator in the case where there are multiple
adjacent uses of a dead basic block from the same user. This fixes PR5596.

Added:
    llvm/trunk/test/Transforms/IPConstantProp/user-with-multiple-uses.ll
Modified:
    llvm/trunk/lib/Transforms/Scalar/SCCP.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SCCP.cpp?rev=89658&r1=89657&r2=89658&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SCCP.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SCCP.cpp Mon Nov 23 10:13:39 2009
@@ -1871,8 +1871,12 @@
       BasicBlock *DeadBB = BlocksToErase[i];
       for (Value::use_iterator UI = DeadBB->use_begin(), UE = DeadBB->use_end();
            UI != UE; ) {
+        // Grab the user and then increment the iterator early, as the user
+        // will be deleted. Step past all adjacent uses from the same user.
+        Instruction *I = dyn_cast<Instruction>(*UI);
+        do { ++UI; } while (UI != UE && *UI == I);
+
         // Ignore blockaddress users; BasicBlock's dtor will handle them.
-        Instruction *I = dyn_cast<Instruction>(*UI++);
         if (!I) continue;
 
         bool Folded = ConstantFoldTerminator(I->getParent());

Added: llvm/trunk/test/Transforms/IPConstantProp/user-with-multiple-uses.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IPConstantProp/user-with-multiple-uses.ll?rev=89658&view=auto

==============================================================================
--- llvm/trunk/test/Transforms/IPConstantProp/user-with-multiple-uses.ll (added)
+++ llvm/trunk/test/Transforms/IPConstantProp/user-with-multiple-uses.ll Mon Nov 23 10:13:39 2009
@@ -0,0 +1,30 @@
+; RUN: opt < %s -S -ipsccp | FileCheck %s
+; PR5596
+
+; IPSCCP should propagate the 0 argument, eliminate the switch, and propagate
+; the result.
+
+; CHECK: define i32 @main() noreturn nounwind {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: %call2 = tail call i32 @wwrite(i64 0) nounwind
+; CHECK-NEXT: ret i32 123
+
+define i32 @main() noreturn nounwind {
+entry:
+  %call2 = tail call i32 @wwrite(i64 0) nounwind
+  ret i32 %call2
+}
+
+define internal i32 @wwrite(i64 %i) nounwind readnone {
+entry:
+  switch i64 %i, label %sw.default [
+    i64 3, label %return
+    i64 10, label %return
+  ]
+
+sw.default:
+  ret i32 123
+
+return:
+  ret i32 0
+}