[llvm][fatlto] Drop any CFI related instrumentation after emitting bitcode (llvm#112788)

We want to support CFI instrumentation for the bitcode section, without
miscompiling the object code portion of a FatLTO object. We can reuse
the existing mechanisms in the LowerTypeTestsPass to do that, by just
adding the pass to the FatLTO pipeline after the EmbedBitcodePass with
the correct options set.

Fixes llvm#112053

Author: ilovepi

clang/test/CodeGen/fat-lto-objects-cfi.cpp

@@ -0,0 +1,46 @@
+// REQUIRES: x86-registered-target
+
+// RUN: %clang_cc1 -triple x86_64-unknown-fuchsia -O2 -flto -ffat-lto-objects \
+// RUN:          -fsanitize=cfi-icall -fsanitize-trap=cfi-icall -fvisibility=hidden  -emit-llvm -o - %s \
+// RUN:   | FileCheck %s
+
+// CHECK: llvm.embedded.object
+// CHECK-SAME: section ".llvm.lto"
+
+// CHECK-LABEL: define hidden void @foo
+//      CHECK: entry:
+// CHECK-NEXT:   %cmp14.not = icmp eq i64 %len, 0
+// CHECK-NEXT:   br i1 %cmp14.not, label %for.end7, label %for.cond1.preheader.preheader
+//      CHECK: for.cond1.preheader.preheader:                    ; preds = %entry
+// CHECK-NEXT:   %arrayidx.1 = getelementptr inbounds nuw i8, ptr %ptr, i64 4
+// CHECK-NEXT:   br label %for.cond1.preheader
+
+// CHECK-NOT: @llvm.type.test
+
+// The code below is a reduced case from https://github.com/llvm/llvm-project/issues/112053
+#define __PRINTFLIKE(__fmt, __varargs) __attribute__((__format__(__printf__, __fmt, __varargs)))
+typedef void func(void* arg, const char* fmt, ...) __PRINTFLIKE(2, 3);
+typedef __SIZE_TYPE__ size_t;
+typedef unsigned long uintptr_t;
+
+extern "C"
+void foo(const void* ptr, size_t len, long disp_addr,
+                     func* printf_func, void* printf_arg) {
+  uintptr_t address = (uintptr_t)ptr;
+  size_t count;
+
+  for (count = 0; count < len; count += 16) {
+    union {
+      unsigned int buf[4];
+      unsigned char cbuf[16];
+    } u;
+    size_t s = 10;
+    size_t i;
+
+    for (i = 0; i < s / 4; i++) {
+      u.buf[i] = ((const unsigned int*)address)[i];
+      printf_func(printf_arg, "%08x ", static_cast<unsigned int>(u.buf[i]));
+    }
+  }
+}
+

llvm/lib/Passes/PassBuilderPipelines.cpp

@@ -1630,6 +1630,13 @@ PassBuilder::buildFatLTODefaultPipeline(OptimizationLevel Level, bool ThinLTO,
     MPM.addPass(buildLTOPreLinkDefaultPipeline(Level));
   MPM.addPass(EmbedBitcodePass(ThinLTO, EmitSummary));
 
+  // If we're doing FatLTO w/ CFI enabled, we don't want the type tests in the
+  // object code, only in the bitcode section, so drop it before we run
+  // module optimization and generate machine code. If llvm.type.test() isn't in
+  // the IR, this won't do anything.
+  MPM.addPass(
+      LowerTypeTestsPass(nullptr, nullptr, lowertypetests::DropTestKind::All));
+
   // Use the ThinLTO post-link pipeline with sample profiling
   if (ThinLTO && PGOOpt && PGOOpt->Action == PGOOptions::SampleUse)
     MPM.addPass(buildThinLTODefaultPipeline(Level, /*ImportSummary=*/nullptr));