[llvm-commits] [llvm] r131919 - in /llvm/trunk: lib/Transforms/Scalar/LoopStrengthReduce.cpp test/CodeGen/X86/lsr-overflow.ll

[Dan Gohman]

Author: djg
Date: Mon May 23 16:07:39 2011
New Revision: 131919

URL: http://llvm.org/viewvc/llvm-project?rev=131919&view=rev
Log:
When checking for signed multiplication overflow, watch out for INT_MIN and -1.
This fixes PR9845.

Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
    llvm/trunk/test/CodeGen/X86/lsr-overflow.ll

Modified: llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp?rev=131919&r1=131918&r2=131919&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp Mon May 23 16:07:39 2011
@@ -2522,6 +2522,8 @@
 
     // Check that multiplying with the unfolded offset doesn't overflow.
     if (F.UnfoldedOffset != 0) {
+      if (F.UnfoldedOffset == INT64_MIN && Factor == -1)
+        continue;
       F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
       if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
         continue;

Modified: llvm/trunk/test/CodeGen/X86/lsr-overflow.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/lsr-overflow.ll?rev=131919&r1=131918&r2=131919&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/lsr-overflow.ll (original)
+++ llvm/trunk/test/CodeGen/X86/lsr-overflow.ll Mon May 23 16:07:39 2011
@@ -25,3 +25,21 @@
   %cmp = icmp eq i64 %indvar, 9223372036854775807
   ret i1 %cmp
 }
+
+define void @func_37() noreturn nounwind readonly {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.inc8, %entry
+  %indvar = phi i64 [ 0, %entry ], [ %indvar.next, %for.inc8 ]
+  %sub.i = add i64 undef, %indvar
+  %cmp.i = icmp eq i64 %sub.i, -9223372036854775808
+  br i1 undef, label %for.inc8, label %for.cond4
+
+for.cond4:                                        ; preds = %for.cond4, %for.body
+  br label %for.cond4
+
+for.inc8:                                         ; preds = %for.body
+  %indvar.next = add i64 %indvar, 1
+  br label %for.body
+}