http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51783
Bug #: 51783 Summary: Missed optimization for X ==/!= (signed type) ((unsigned type) Y + Z) Classification: Unclassified Product: gcc Version: 4.7.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization AssignedTo: unassig...@gcc.gnu.org ReportedBy: kti...@gcc.gnu.org Target: *-*-* Hi, for the following example shows the missed optimization extern int ar[256]; int foo (int x, int y, unsigned int z) { int c = (int) ((unsigned int) x + z); return y == c; } We produce in 4.7 for -O2 the following optimized gimple tree: ;; Function foo (foo, funcdef_no=0, decl_uid=1601, cgraph_uid=0) foo (int x, int y, unsigned int z) { int c; _Bool D.2717; int D.2716; unsigned int D.2715; unsigned int x.0; <bb 2>: x.0_2 = (unsigned int) x_1(D); D.2715_4 = z_3(D) + x.0_2; c_5 = (int) D.2715_4; D.2717_7 = y_6(D) == c_5; D.2716_8 = (int) D.2717_7; return D.2716_8; } But we could expect in this case: ;; Function foo (foo, funcdef_no=0, decl_uid=1710, cgraph_uid=0) foo (int x, int y, unsigned int z) { int D.1720; int c; _Bool D.1717; int D.1716; <bb 2>: D.1720_10 = (int) z_3(D); c_5 = x_1(D) + D.1720_10; D.1717_7 = y_6(D) == c_5; D.1716_8 = (int) D.1717_7; return D.1716_8; }