6 Commits

Author	SHA1	Message	Date
Benjamin Kramer	e4853baa4b	InstCombine: Turn (zext A) udiv (zext B) into (zext (A udiv B)). Same for urem or constant B. ... This obviously helps a lot if the division would be turned into a libcall (think i64 udiv on i386), but div is also one of the few remaining instructions on modern CPUs that become more expensive when the bitwidth gets bigger. This also helps register pressure on i386 when dividing chars, divb needs two 8-bit parts of a 16 bit register as input where divl uses two registers. int foo(unsigned char a) { return a/10; } int bar(unsigned char a, unsigned char b) { return a/b; } compiles into (x86_64) _foo: imull $205, %edi, %eax shrl $11, %eax ret _bar: movzbl %dil, %eax divb %sil, %al movzbl %al, %eax ret llvm-svn: 130615	2011-04-30 18:16:07 +00:00
Chris Lattner	c6bb31e5ea	make instcombine only rewrite a chain of computation ... (eliminating some extends) if the new type of the computation is legal or if both the source and dest are illegal. This prevents instcombine from changing big chains of computation into i64 on 32-bit targets for example. llvm-svn: 86398	2009-11-07 19:11:46 +00:00
Dan Gohman	205b641954	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the ... input filename so that opt doesn't print the input filename in the output so that grep lines in the tests don't unintentionally match strings in the input filename. llvm-svn: 81537	2009-09-11 18:01:28 +00:00
Dan Gohman	c95df8b6d8	Use opt -S instead of piping bitcode output through llvm-dis. ... llvm-svn: 81257	2009-09-08 22:34:10 +00:00
Dan Gohman	8d84372836	Change these tests to feed the assembly files to opt directly, instead ... of using llvm-as, now that opt supports this. llvm-svn: 81226	2009-09-08 16:50:01 +00:00
Eli Friedman	a6c7a3d44e	PR4548: optimize zext+udiv+trunc to udiv. ... llvm-svn: 75539	2009-07-13 22:46:01 +00:00