Okay, spiff is completely incapable of handling files of nontrivial size.

Here is a simple minimal program that does what we want.  Instead of taking
minutes to compare mesa's output, and crashing on binary files (like spiff
does), this take < .02s in the common case and doesn't crash.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12926 91177308-0d34-0410-b5e6-96231b3b80d8

utils/fpcmp/Makefile

@@ -0,0 +1,15 @@
+##===- utils/fpcmp/Makefile --------------------------------*- Makefile -*-===##
+# 
+#                     The LLVM Compiler Infrastructure
+#
+# This file was developed by the LLVM research group and is distributed under
+# the University of Illinois Open Source License. See LICENSE.TXT for details.
+# 
+##===----------------------------------------------------------------------===##
+
+LEVEL = ../..
+TOOLNAME = fpcmp
+USEDLIBS = support.a
+
+include $(LEVEL)/Makefile.common
+

utils/fpcmp/fpcmp.cpp

@@ -0,0 +1,156 @@
+//===- fpcmp.cpp - A fuzzy "cmp" that permits floating point noise --------===//
+// 
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// 
+//===----------------------------------------------------------------------===//
+//
+// fpcmp is a tool that basically works like the 'cmp' tool, except that it can
+// tolerate errors due to floating point noise, with the -r option.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Support/CommandLine.h"
+#include "Support/FileUtilities.h"
+#include "Config/fcntl.h"
+#include "Config/sys/mman.h"
+#include <iostream>
+#include <cmath>
+
+using namespace llvm;
+
+namespace {
+  cl::opt<std::string>
+  File1(cl::Positional, cl::desc("<input file #1>"), cl::Required);
+  cl::opt<std::string>
+  File2(cl::Positional, cl::desc("<input file #2>"), cl::Required);
+
+  cl::opt<double>
+  RelTolerance("r", cl::desc("Relative error tolerated"), cl::init(0));
+  cl::opt<double>
+  AbsTolerance("a", cl::desc("Absolute error tolerated"), cl::init(0));
+}
+
+
+/// OpenFile - mmap the specified file into the address space for reading, and
+/// return the length and address of the buffer.
+static void OpenFile(const std::string &Filename, unsigned &Len, char* &BufPtr){
+  int FD = open(Filename.c_str(), O_RDONLY);
+  if (FD == -1 || (Len = getFileSize(Filename)) == ~0U) {
+    std::cerr << "Error: cannot open file '" << Filename << "'\n";
+    exit(2);
+  }
+
+  // mmap in the file all at once...
+  BufPtr = (char*)mmap(0, Len, PROT_READ, MAP_PRIVATE, FD, 0);
+  
+  if (BufPtr == (char*)MAP_FAILED) {
+    std::cerr << "Error: cannot open file '" << Filename << "'\n";
+    exit(2);
+  }
+}
+
+static bool isNumberChar(char C) {
+  switch (C) {
+  case '0': case '1': case '2': case '3': case '4':
+  case '5': case '6': case '7': case '8': case '9': 
+  case '.':
+  case 'e':
+  case 'E': return true;
+  default: return false;
+  }
+}
+
+static char *BackupNumber(char *Pos, char *FirstChar) {
+  while (Pos < FirstChar && isNumberChar(Pos[-1]))
+    --Pos;
+  return Pos;
+}
+
+static void CompareNumbers(char *&F1P, char *&F2P, char *F1End, char *F2End) {
+  char *F1NumEnd, *F2NumEnd;
+  double V1 = strtod(F1P, &F1NumEnd);
+  double V2 = strtod(F2P, &F2NumEnd);
+
+  if (F1NumEnd == F1P || F2NumEnd == F2P) {
+    std::cerr << "Comparison failed, not a numeric difference.\n";
+    exit(1);
+  }
+
+  // Check to see if these are inside the absolute tolerance
+  if (AbsTolerance < std::abs(V1-V2)) {
+    // Nope, check the relative tolerance...
+    double Diff;
+    if (V2)
+      Diff = std::abs(V1/V2 - 1.0);
+    else if (V1)
+      Diff = std::abs(V2/V1 - 1.0);
+    else
+      Diff = 0;  // Both zero.
+    if (Diff > RelTolerance) {
+      std::cerr << "Compared: " << V1 << " and " << V2 << ": diff = "
+                << Diff << "\n";
+      std::cerr << "Out of tolerence: rel/abs: " << RelTolerance
+                << "/" << AbsTolerance << "\n";
+      exit(1);
+    }
+  }
+
+  // Otherwise, advance our read pointers to the end of the numbers.
+  F1P = F1NumEnd;  F2P = F2NumEnd;
+}
+
+
+int main(int argc, char **argv) {
+  cl::ParseCommandLineOptions(argc, argv);
+
+  // mmap in the files.
+  unsigned File1Len, File2Len;
+  char *File1Start, *File2Start;
+  OpenFile(File1, File1Len, File1Start);
+  OpenFile(File2, File2Len, File2Start);
+
+  // Okay, now that we opened the files, scan them for the first difference.
+  char *File1End = File1Start+File1Len;
+  char *File2End = File2Start+File2Len;
+  char *F1P = File1Start;
+  char *F2P = File2Start;
+  
+  while (1) {
+    // Scan for the end of file or first difference.
+    while (F1P < File1End && F2P < File2End && *F1P == *F2P)
+      ++F1P, ++F2P;
+
+    if (F1P >= File1End || F2P >= File2End) break;
+
+    // Okay, we must have found a difference.  Backup to the start of the
+    // current number each stream is at so that we can compare from the
+    // beginning.
+    F1P = BackupNumber(F1P, File1Start);
+    F2P = BackupNumber(F2P, File2Start);
+
+    // Now that we are at the start of the numbers, compare them, exiting if
+    // they don't match.
+    CompareNumbers(F1P, F2P, File1End, File2End);
+  }
+
+  // Okay, we reached the end of file.  If both files are at the end, we
+  // succeeded.
+  if (F1P >= File1End && F2P >= File2End) return 0;
+
+  // Otherwise, we might have run off the end due to a number, backup and retry.
+  F1P = BackupNumber(F1P, File1Start);
+  F2P = BackupNumber(F2P, File2Start);
+
+  // Now that we are at the start of the numbers, compare them, exiting if
+  // they don't match.
+  CompareNumbers(F1P, F2P, File1End, File2End);
+
+  // If we found the end, we succeeded.
+  if (F1P >= File1End && F2P >= File2End) return 0;
+
+  return 1;
+}
+