[llvm] [compiler-rt] [IRPGO][ValueProfile] Instrument virtual table address that could be used to do virtual table address comparision for indirect-call-promotion. (PR #66825)

[Snehasish Kumar via llvm-commits]

================
@@ -0,0 +1,83 @@
+#!/bin/bash
+
+if [ $# -lt 2 ]; then
+  echo "Path to clang++ required!"
+  echo "Usage: update_vtable_value_prof_inputs.sh /path/to/updated/clang++"
+  exit 1
+else
+  CLANG=$1
+fi
+
+OUTDIR=$(dirname $(realpath -s $0))
+
+echo "Outdir is $OUTDIR"
+
+cat > ${OUTDIR}/vtable_prof.cc << EOF
+#include <cstdlib>
+#include <cstdio>
+
+class Base {
+ public:
+  virtual int func1(int a, int b) = 0;
+  virtual int func2(int a, int b) = 0;
+};
+
+class Derived1 : public Base {
+    public:
+    __attribute__((noinline))
+    int func1(int a, int b) override
+    {
+        return a + b;
+    }
+
+    __attribute__((noinline))
+    int func2(int a, int b) override {
+        return a * b;
+    }
+};
+
+class Derived2 : public Base {
+    public:
+    
+    __attribute__((noinline))
+    int func1(int a, int b) override {
+        return a - b;
+    }
+
+    __attribute__((noinline))
+    int func2(int a, int b) override {
+        return a * (a - b);
+    }
+};
+
+__attribute__((noinline)) Base* createType(int a) {
+    Base* base = nullptr;
+    if (a % 4 == 0)
+      base = new Derived1();
+    else
+      base = new Derived2();
+    return base;
+}
+
+
+int main(int argc, char** argv) {
+    int sum = 0;
+    for (int i = 0; i < 1000; i++) {
+        int a = rand();
+        int b = rand();
+        Base* ptr = createType(i);
+        sum += ptr->func1(a, b) + ptr->func2(b, a);
+    }
+    printf("sum is %d\n", sum);
+    return 0;
+}
+EOF
+
+FLAGS="-fuse-ld=lld -O2 -g -fprofile-generate=. -flto=thin -Xclang -fwhole-program-vtables -Wl,--lto-whole-program-visibility"
----------------
snehasish wrote:

This invocation still uses -fwhole-program-vtables. I think the reliance on type test was removed in the last commit?

https://github.com/llvm/llvm-project/pull/66825