Initial commit

Author: sanjoy

.gitignore

@@ -0,0 +1,5 @@
+/*.ll
+/*.o
+/order-a
+/order-b
+/order-c

build.sh

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+#!/bin/bash
+
+CLANG=clang++
+COMPILE_OPTS='-c -Wall -Werror -O3'
+
+${CLANG} -v
+
+${CLANG} ${COMPILE_OPTS} source-a.cpp -o source-a.o
+${CLANG} ${COMPILE_OPTS} source-b.cpp -o source-b.o
+${CLANG} ${COMPILE_OPTS} main.cpp     -o main.o
+
+${CLANG} ${COMPILE_OPTS} source-a.cpp -emit-llvm -S -o source-a.ll
+${CLANG} ${COMPILE_OPTS} source-b.cpp -emit-llvm -S -o source-b.ll
+${CLANG} ${COMPILE_OPTS} main.cpp     -emit-llvm -S -o main.ll
+
+${CLANG} main.o source-b.o source-a.o -o order-a
+${CLANG} main.o source-a.o source-b.o -o order-b
+${CLANG} source-a.o source-b.o main.o -o order-c

header.hpp

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+#ifndef __HEADER_HPP
+#define __HEADER_HPP
+
+#include <cstdint>
+
+struct IntegerPair;
+
+bool always_false(unsigned);
+
+inline unsigned __attribute__((noinline)) maybe_divide(unsigned *ptr) {
+  unsigned val = 500 / ptr[0];
+  if (always_false(val))
+    return val;
+  return (unsigned)((intptr_t)ptr);
+}
+
+#endif // __HEADER_HPP

main.cpp

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+#include <cstdlib>
+
+unsigned caller_a(unsigned *ptr);
+
+int main() {
+  unsigned *ptr = new unsigned[1];
+  ptr[0] = 0;
+  caller_a(ptr);
+  delete[] ptr;
+  return 0;
+}

source-a.cpp

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+#include "header.hpp"
+
+bool always_false(unsigned) { return false; }
+
+unsigned caller_a(unsigned *ptr) {
+  ptr[0] = 10;
+  unsigned k = maybe_divide(ptr);
+  ptr[0] = 20;
+  return k;
+}

source-b.cpp

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+#include "header.hpp"
+
+unsigned caller_b(unsigned *ptr) {
+  ptr[0] = 10;
+  unsigned k = maybe_divide(ptr);
+  ptr[0] = 20;
+  return k;
+}