[llvm] r185218 - Eliminate an assortment of undefined behavior.

[Jakob Stoklund Olesen]

Author: stoklund
Date: Fri Jun 28 16:10:25 2013
New Revision: 185218

URL: http://llvm.org/viewvc/llvm-project?rev=185218&view=rev
Log:
Eliminate an assortment of undefined behavior.

Hopefully, this fixes the PPC64 buildbots.

Modified:
    llvm/trunk/lib/Support/BlockFrequency.cpp

Modified: llvm/trunk/lib/Support/BlockFrequency.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/BlockFrequency.cpp?rev=185218&r1=185217&r2=185218&view=diff
==============================================================================
--- llvm/trunk/lib/Support/BlockFrequency.cpp (original)
+++ llvm/trunk/lib/Support/BlockFrequency.cpp Fri Jun 28 16:10:25 2013
@@ -47,9 +47,13 @@ static uint64_t div96bit(uint64_t W[2],
   uint64_t x = W[1];
   unsigned i;
 
+  // This is really a 64-bit division.
+  if (!x)
+    return y / D;
+
   // This long division algorithm automatically saturates on overflow.
   for (i = 0; i < 64 && x; ++i) {
-    uint32_t t = (int)x >> 31;
+    uint32_t t = -((x >> 31) & 1); // Splat bit 31 to bits 0-31.
     x = (x << 1) | (y >> 63);
     y = y << 1;
     if ((x | t) >= D) {