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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - X86: Tail calls with function pointer indirection not folded when more than 1 parameter is passed"
href="https://bugs.llvm.org/show_bug.cgi?id=50042">50042</a>
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<th>Summary</th>
<td>X86: Tail calls with function pointer indirection not folded when more than 1 parameter is passed
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>mejedi@gmail.com
</td>
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<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, pengfei.wang@intel.com, spatel+llvm@rotateright.com
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<pre>Created <span class=""><a href="attachment.cgi?id=24774" name="attach_24774" title="reproducer">attachment 24774</a> <a href="attachment.cgi?id=24774&action=edit" title="reproducer">[details]</a></span>
reproducer
The following snippet produces the assembly with function pointer table
indexing folded into JMP:
typedef void (*FnTy3) (void *);
void dispatch15(FnTy3 *tab, intptr_t i) {
tab[i](tab);
}
_dispatch15: ## @dispatch15
## %bb.0: ## %entry
jmpq *(%rdi,%rsi,8) ## TAILCALL
If the called function takes at least 2 parameters, indexing isn't folded.
typedef void (*FnTy2) (void *, intptr_t);
void dispatch1(FnTy2 *tab, intptr_t i) {
tab[i](tab, i);
}
_dispatch1: ## @dispatch1
## %bb.0: ## %entry
movq (%rdi,%rsi,8), %rax
jmpq *%rax ## TAILCALL</pre>
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