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[MergeFunctions] Replace all uses of unnamed_addr functions.

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This reduces code size for constructs like vtables or interrupt
tables that refer to functions in global initializers.

Differential Revision: https://reviews.llvm.org/D34805

llvm-svn: 315852
This commit is contained in:
whitequark 2017-10-15 12:29:01 +00:00
parent e7217f408e
commit f431f04c96
3 changed files with 57 additions and 3 deletions
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6
lib/Transforms/IPO/MergeFunctions.cpp
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@ -628,10 +628,16 @@ void MergeFunctions::filterInstsUnrelatedToPDI(
// call sites to point to F even when within the same translation unit.
void MergeFunctions::writeThunk(Function *F, Function *G) {
if (!G->isInterposable() && !MergeFunctionsPDI) {
if (G->hasGlobalUnnamedAddr()) {
// If G's address is not significant, replace it entirely.
Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
G->replaceAllUsesWith(BitcastF);
} else {
// Redirect direct callers of G to F. (See note on MergeFunctionsPDI
// above).
replaceDirectCallers(G, F);
}
}
// If G was internal then we may have replaced all uses of G with F. If so,
// stop here and delete G. There's no need for a thunk. (See note on

30
test/Transforms/MergeFunc/merge-unnamed-addr-bitcast.ll Normal file
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@ -0,0 +1,30 @@
; RUN: opt -S -mergefunc < %s | FileCheck %s
%A = type { i32 }
%B = type { i32 }
; CHECK-NOT: @b
@x = constant { i32 (i32)*, i32 (i32)* }
{ i32 (i32)* bitcast (i32 (%A)* @a to i32 (i32)*),
i32 (i32)* bitcast (i32 (%B)* @b to i32 (i32)*) }
; CHECK: { i32 (i32)* bitcast (i32 (%A)* @a to i32 (i32)*), i32 (i32)* bitcast (i32 (%A)* @a to i32 (i32)*) }
define internal i32 @a(%A) unnamed_addr {
extractvalue %A %0, 0
xor i32 %2, 0
ret i32 %3
}
define internal i32 @b(%B) unnamed_addr {
extractvalue %B %0, 0
xor i32 %2, 0
ret i32 %3
}
define i32 @c(i32) {
insertvalue %B undef, i32 %0, 0
call i32 @b(%B %2)
; CHECK: call i32 bitcast (i32 (%A)* @a to i32 (%B)*)(%B %2)
ret i32 %3
}

18
test/Transforms/MergeFunc/merge-unnamed-addr.ll Normal file
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@ -0,0 +1,18 @@
; RUN: opt -S -mergefunc < %s | FileCheck %s
; CHECK-NOT: @b
@x = constant { i32 (i32)*, i32 (i32)* } { i32 (i32)* @a, i32 (i32)* @b }
; CHECK: { i32 (i32)* @a, i32 (i32)* @a }
define internal i32 @a(i32 %a) unnamed_addr {
%b = xor i32 %a, 0
%c = xor i32 %b, 0
ret i32 %c
}
define internal i32 @b(i32 %a) unnamed_addr {
%b = xor i32 %a, 0
%c = xor i32 %b, 0
ret i32 %c
}