Make emission of 'if' conditions much more sophisticated when we
have a condition that is an &&/||. Before we used to compile things like this:
int test() {
if (x && y) foo(); else bar();
}
into:
%0 = load i32* @x ; <i32> [#uses=1]
%1 = icmp ne i32 %0, 0 ; <i1> [#uses=1]
br i1 %1, label %land_rhs, label %land_cont
land_rhs: ; preds = %entry
%2 = load i32* @y ; <i32> [#uses=1]
%3 = icmp ne i32 %2, 0 ; <i1> [#uses=1]
br label %land_cont
land_cont: ; preds = %land_rhs, %entry
%4 = phi i1 [ false, %entry ], [ %3, %land_rhs ] ; <i1> [#uses=1]
br i1 %4, label %ifthen, label %ifelse
ifthen: ; preds = %land_cont
%call = call i32 (...)* @foo() ; <i32> [#uses=0]
br label %ifend
ifelse: ; preds = %land_cont
%call1 = call i32 (...)* @bar() ; <i32> [#uses=0]
br label %ifend
ifend: ; preds = %ifelse, %ifthen
Now we turn it into the much more svelte code:
%0 = load i32* @x ; <i32> [#uses=1]
%1 = icmp ne i32 %0, 0 ; <i1> [#uses=1]
br i1 %1, label %land_lhs_true, label %ifelse
land_lhs_true: ; preds = %entry
%2 = load i32* @y ; <i32> [#uses=1]
%3 = icmp ne i32 %2, 0 ; <i1> [#uses=1]
br i1 %3, label %ifthen, label %ifelse
ifthen: ; preds = %land_lhs_true
%call = call i32 (...)* @foo() ; <i32> [#uses=0]
br label %ifend
ifelse: ; preds = %land_lhs_true, %entry
%call1 = call i32 (...)* @bar() ; <i32> [#uses=0]
br label %ifend
ifend: ; preds = %ifelse, %ifthen
Note the lack of a phi node.
This shrinks the -O0 .ll file for 176.gcc/expr.c from 43176 to 40267 lines.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@59111 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed