improve CreateCoercedLoad a bit to generate slightly less awful
IR when handling X86-64 by-value struct stuff. For example, we
use to compile this:
struct DeclGroup {
unsigned NumDecls;
};
int foo(DeclGroup D);
void bar(DeclGroup *D) {
foo(*D);
}
into:
define void @_Z3barP9DeclGroup(%struct.DeclGroup* %D) ssp nounwind {
entry:
%D.addr = alloca %struct.DeclGroup*, align 8 ; <%struct.DeclGroup**> [#uses=2]
%agg.tmp = alloca %struct.DeclGroup, align 4 ; <%struct.DeclGroup*> [#uses=2]
%tmp3 = alloca i64 ; <i64*> [#uses=2]
store %struct.DeclGroup* %D, %struct.DeclGroup** %D.addr
%tmp = load %struct.DeclGroup** %D.addr ; <%struct.DeclGroup*> [#uses=1]
%tmp1 = bitcast %struct.DeclGroup* %agg.tmp to i8* ; <i8*> [#uses=1]
%tmp2 = bitcast %struct.DeclGroup* %tmp to i8* ; <i8*> [#uses=1]
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %tmp1, i8* %tmp2, i64 4, i32 4, i1 false)
%0 = bitcast i64* %tmp3 to %struct.DeclGroup* ; <%struct.DeclGroup*> [#uses=1]
%1 = load %struct.DeclGroup* %agg.tmp ; <%struct.DeclGroup> [#uses=1]
store %struct.DeclGroup %1, %struct.DeclGroup* %0, align 1
%2 = load i64* %tmp3 ; <i64> [#uses=1]
call void @_Z3foo9DeclGroup(i64 %2)
ret void
}
which would cause fastisel to bail out due to the first class aggregate load %1. With
this patch we now compile it into the (still awful):
define void @_Z3barP9DeclGroup(%struct.DeclGroup* %D) nounwind ssp noredzone {
entry:
%D.addr = alloca %struct.DeclGroup*, align 8 ; <%struct.DeclGroup**> [#uses=2]
%agg.tmp = alloca %struct.DeclGroup, align 4 ; <%struct.DeclGroup*> [#uses=2]
%tmp3 = alloca i64 ; <i64*> [#uses=2]
store %struct.DeclGroup* %D, %struct.DeclGroup** %D.addr
%tmp = load %struct.DeclGroup** %D.addr ; <%struct.DeclGroup*> [#uses=1]
%tmp1 = bitcast %struct.DeclGroup* %agg.tmp to i8* ; <i8*> [#uses=1]
%tmp2 = bitcast %struct.DeclGroup* %tmp to i8* ; <i8*> [#uses=1]
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %tmp1, i8* %tmp2, i64 4, i32 4, i1 false)
%coerce.dive = getelementptr %struct.DeclGroup* %agg.tmp, i32 0, i32 0 ; <i32*> [#uses=1]
%0 = bitcast i64* %tmp3 to i32* ; <i32*> [#uses=1]
%1 = load i32* %coerce.dive ; <i32> [#uses=1]
store i32 %1, i32* %0, align 1
%2 = load i64* %tmp3 ; <i64> [#uses=1]
%call = call i32 @_Z3foo9DeclGroup(i64 %2) noredzone ; <i32> [#uses=0]
ret void
}
which doesn't bail out. On CGStmt.ll, this reduces fastisel bail outs from 958 to 935,
and is the precursor of better things to come.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@106973 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed