The basic problem is that some mainstream programs cannot deal with the way
clang optimizes tail calls, as in this example: int foo(void); int bar(void) { return foo(); } where the call is transformed to: calll .L0$pb .L0$pb: popl %eax .Ltmp0: addl $_GLOBAL_OFFSET_TABLE_+(.Ltmp0-.L0$pb), %eax movl foo@GOT(%eax), %eax popl %ebp jmpl *%eax # TAILCALL However, the GOT references must all be resolved at dlopen() time, and so this approach cannot be used with lazy dynamic linking (e.g. using RTLD_LAZY), which usually populates the PLT with stubs that perform the actual resolving. This patch changes X86TargetLowering::LowerCall() to skip tail call optimization, if the called function is a global or external symbol. Patch by Dimitry Andric! PR15086 llvm-svn: 195318
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