[llvm-commits] [llvm] r122814 - in /llvm/trunk: lib/Analysis/ValueTracking.cpp test/Transforms/InstCombine/crash.ll

[Chris Lattner]

Author: lattner
Date: Tue Jan  4 12:19:15 2011
New Revision: 122814

URL: http://llvm.org/viewvc/llvm-project?rev=122814&view=rev
Log:
fix an off-by-one bug that caused a crash analyzing
ashr's with huge shift amounts, PR8896

Modified:
    llvm/trunk/lib/Analysis/ValueTracking.cpp
    llvm/trunk/test/Transforms/InstCombine/crash.ll

Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=122814&r1=122813&r2=122814&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Tue Jan  4 12:19:15 2011
@@ -337,7 +337,7 @@
     // (ashr X, C1) & C2 == 0   iff  (-1 >> C1) & C2 == 0
     if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
       // Compute the new bits that are at the top now.
-      uint64_t ShiftAmt = SA->getLimitedValue(BitWidth);
+      uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1);
       
       // Signed shift right.
       APInt Mask2(Mask.shl(ShiftAmt));

Modified: llvm/trunk/test/Transforms/InstCombine/crash.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/crash.ll?rev=122814&r1=122813&r2=122814&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/crash.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/crash.ll Tue Jan  4 12:19:15 2011
@@ -298,3 +298,40 @@
 }
 
 
+; PR8896
+ at g_54 = external global [7 x i16]
+
+define void @test15(i32* %p_92) nounwind {
+entry:
+%0 = load i32* %p_92, align 4
+%1 = icmp ne i32 %0, 0
+%2 = zext i1 %1 to i32
+%3 = call i32 @func_14() nounwind
+%4 = trunc i32 %3 to i16
+%5 = sext i16 %4 to i32
+%6 = trunc i32 %5 to i16
+br i1 undef, label %"3", label %"5"
+
+"3":                                              ; preds = %entry
+%7 = sext i16 %6 to i32
+%8 = ashr i32 %7, -1649554541
+%9 = trunc i32 %8 to i16
+br label %"5"
+
+"5":                                              ; preds = %"3", %entry
+%10 = phi i16 [ %9, %"3" ], [ %6, %entry ]
+%11 = sext i16 %10 to i32
+%12 = xor i32 %2, %11
+%13 = sext i32 %12 to i64
+%14 = icmp ne i64 %13, 0
+br i1 %14, label %return, label %"7"
+
+"7":                                              ; preds = %"5"
+ret void
+
+return:                                           ; preds = %"5"
+ret void
+}
+
+declare i32 @func_14()
+