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4f1134e51a
(familiar) function:
int _strlen(const char *str) {
int len = 0;
while (*str++) len++;
return len;
}
And transforming it to use a ulong induction variable, because the type of
the pointer index was left as a constant long. This is obviously very bad.
The fix is to shrink long constants in getelementptr instructions to intptr_t,
making the indvars pass insert a uint induction variable, which is much more
efficient.
Here's the before code for this function:
int %_strlen(sbyte* %str) {
entry:
%tmp.13 = load sbyte* %str ; <sbyte> [#uses=1]
%tmp.24 = seteq sbyte %tmp.13, 0 ; <bool> [#uses=1]
br bool %tmp.24, label %loopexit, label %no_exit
no_exit: ; preds = %entry, %no_exit
*** %indvar = phi uint [ %indvar.next, %no_exit ], [ 0, %entry ] ; <uint> [#uses=2]
*** %indvar = phi ulong [ %indvar.next, %no_exit ], [ 0, %entry ] ; <ulong> [#uses=2]
%indvar1 = cast ulong %indvar to uint ; <uint> [#uses=1]
%inc.02.sum = add uint %indvar1, 1 ; <uint> [#uses=1]
%inc.0.0 = getelementptr sbyte* %str, uint %inc.02.sum ; <sbyte*> [#uses=1]
%tmp.1 = load sbyte* %inc.0.0 ; <sbyte> [#uses=1]
%tmp.2 = seteq sbyte %tmp.1, 0 ; <bool> [#uses=1]
%indvar.next = add ulong %indvar, 1 ; <ulong> [#uses=1]
%indvar.next = add uint %indvar, 1 ; <uint> [#uses=1]
br bool %tmp.2, label %loopexit.loopexit, label %no_exit
loopexit.loopexit: ; preds = %no_exit
%indvar = cast uint %indvar to int ; <int> [#uses=1]
%inc.1 = add int %indvar, 1 ; <int> [#uses=1]
ret int %inc.1
loopexit: ; preds = %entry
ret int 0
}
Here's the after code:
int %_strlen(sbyte* %str) {
entry:
%inc.02 = getelementptr sbyte* %str, uint 1 ; <sbyte*> [#uses=1]
%tmp.13 = load sbyte* %str ; <sbyte> [#uses=1]
%tmp.24 = seteq sbyte %tmp.13, 0 ; <bool> [#uses=1]
br bool %tmp.24, label %loopexit, label %no_exit
no_exit: ; preds = %entry, %no_exit
*** %indvar = phi uint [ %indvar.next, %no_exit ], [ 0, %entry ] ; <uint> [#uses=3]
%indvar = cast uint %indvar to int ; <int> [#uses=1]
%inc.0.0 = getelementptr sbyte* %inc.02, uint %indvar ; <sbyte*> [#uses=1]
%inc.1 = add int %indvar, 1 ; <int> [#uses=1]
%tmp.1 = load sbyte* %inc.0.0 ; <sbyte> [#uses=1]
%tmp.2 = seteq sbyte %tmp.1, 0 ; <bool> [#uses=1]
%indvar.next = add uint %indvar, 1 ; <uint> [#uses=1]
br bool %tmp.2, label %loopexit, label %no_exit
loopexit: ; preds = %entry, %no_exit
%len.0.1 = phi int [ 0, %entry ], [ %inc.1, %no_exit ] ; <int> [#uses=1]
ret int %len.0.1
}
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@13016 91177308-0d34-0410-b5e6-96231b3b80d8
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