problem reported on cfe-dev.

llvm-svn: 130661

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

This folds away silly stuff like (a&255)/1000 -> 0.

llvm-svn: 130614

llvm-svn: 130551

llvm-svn: 130536

llvm-svn: 130528

llvm-svn: 130527

llvm-svn: 130526

llvm-svn: 130489

Fixes PR9809.

llvm-svn: 130485

llvm-svn: 130450

This shouldn't happen in practice because the icmp would be a constant.
Add a check so we don't miscompile code if something goes wrong.

llvm-svn: 130446

between two reads (threading).

Fix an off-by-one in the indirect counter table that I meant to revert after an
earlier experiment. Whoops!

Implement GCOV_PREFIX. Doesn't handle GCOV_PREFIX_STRIP yet.

Fix an off-by-one in string emission. Extra whoops!

Tolerate DISubprograms that have null Function*'s attached to them. I don't yet
understand what this means, but it happens when you have a global static with
a non-trivial constructor/destructor.

Fix a crash on switch statements with a single successor (default-only).

llvm-svn: 130443

llvm-svn: 130431

llvm-svn: 130428

llvm-svn: 130426

llvm-svn: 130419

a nice and tidy:
  %x1 = load i32* %0, align 4
  %1 = icmp eq i32 %x1, 1179403647
  br i1 %1, label %if.then, label %if.end

instead of doing lots of loads and branches.  May the FreeBSD bootloader
long fit in its allocated space.

llvm-svn: 130416

llvm-svn: 130414

llvm-svn: 130408

This happens when GVN widens loads. Part of PR6627.

llvm-svn: 130405

static functions instead of passing around tons of random ivars.

llvm-svn: 130403

llvm-svn: 130401

wider load would allow elimination of subsequent loads, and when the wider
load is still a native integer type.  This eliminates a ton of loads on 
various benchmarks involving struct fields, though it is somewhat hobbled
by clang not being very aggressive about field alignment.

This is yet another step along the way towards resolving PR6627.

llvm-svn: 130390

llvm-svn: 130350

Modified LinearFunctionTestReplace to push the condition on the dead
list instead of eagerly deleting it. This can cause unnecessary
IV rewrites, which should have no effect on codegen and will not be an
issue once we stop generating canonical IVs.

llvm-svn: 130340

Simplify cfg inserts a call to trap when unreachable code is detected. Assign DebugLoc to this new trap instruction.

llvm-svn: 130315

effective in avoiding recomputation of LCSSA form; the widespread
use of instsimplify (which looks through phi nodes) means it was
not preserving LCSSA form anyway; and instcombine is no longer
scheduled in the middle of the loop passes so this doesn't matter
anymore.

llvm-svn: 130301

when X has multiple uses.  This is useful for exposing secondary optimizations,
but the X86 backend isn't ready for this when X has a single use.  For example,
this can disable load folding.

This is inching towards resolving PR6627.

llvm-svn: 130238

llvm-svn: 130237

translation fails.  We were bailing out in some cases that would
cause us to miss GVN'ing some non-local cases away.

llvm-svn: 130206

Add support for switch and indirectbr edges. This works by densely numbering
all blocks which have such terminators, and then separately numbering the
possible successors. The predecessors write down a number, the successor knows
its own number (as a ConstantInt) and sends that and the pointer to the number
the predecessor wrote down to the runtime, who looks up the counter in a
per-function table.

Coverage data should now be functional, but I haven't tested it on anything
other than my 2-file synthetic test program for coverage.

llvm-svn: 130186

return it as a clobber.  This allows GVN to do smart things.

Enhance GVN to be smart about the case when a small load is clobbered
by a larger overlapping load.  In this case, forward the value.  This
allows us to compile stuff like this:

int test(void *P) {
  int tmp = *(unsigned int*)P;
  return tmp+*((unsigned char*)P+1);
}

into:

_test:                                  ## @test
	movl	(%rdi), %ecx
	movzbl	%ch, %eax
	addl	%ecx, %eax
	ret

which has one load.  We already handled the case where the smaller
load was from a must-aliased base pointer.

llvm-svn: 130180

llvm-svn: 130068

llvm-svn: 129932

necessary since gcov counts transitions between blocks. It can't see if you've
run every line in a straight-line function, so we add an edge for it to notice.

llvm-svn: 129905

comment for 80 columns.

llvm-svn: 129904

instrument the program to emit .gcda.
TODO: we should emit slightly different .gcda files when .gcno emission is off.

llvm-svn: 129903

generated by llvm-gcc, since llvm-gcc uses 2 i64s for passing a 4 x float
vector on ARM rather than an i64 array like Clang.

llvm-svn: 129878

delete it.

llvm-svn: 129877