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Revert r185257 (InstCombine: Be more agressive optimizing 'udiv' instrs with 'select' denoms)

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I'm reverting this commit because:

 1. As discussed during review, it needs to be rewritten (to avoid creating and
then deleting instructions).

 2. This is causing optimizer crashes. Specifically, I'm seeing things like
this:

    While deleting: i1 %
    Use still stuck around after Def is destroyed:  <badref> = select i1 <badref>, i32 0, i32 1
    opt: /src/llvm-trunk/lib/IR/Value.cpp:79: virtual llvm::Value::~Value(): Assertion `use_empty() && "Uses remain when a value is destroyed!"' failed.

   I'd guess that these will go away once we're no longer creating/deleting
instructions here, but just in case, I'm adding a regression test.

Because the code is bring rewritten, I've just XFAIL'd the original regression test. Original commit message:

	InstCombine: Be more agressive optimizing 'udiv' instrs with 'select' denoms

	Real world code sometimes has the denominator of a 'udiv' be a
	'select'.  LLVM can handle such cases but only when the 'select'
	operands are symmetric in structure (both select operands are a constant
	power of two or a left shift, etc.).  This falls apart if we are dealt a
	'udiv' where the code is not symetric or if the select operands lead us
	to more select instructions.

	Instead, we should treat the LHS and each select operand as a distinct
	divide operation and try to optimize them independently.  If we can
	to simplify each operation, then we can replace the 'udiv' with, say, a
	'lshr' that has a new select with a bunch of new operands for the
	select.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185415 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel
2013-07-02 05:21:11 +00:00
parent e7dd3afef0
commit b19dd2bcaf
3 changed files with 158 additions and 89 deletions
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101
test/Transforms/InstCombine/div-shift-crash.ll Normal file
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@@ -0,0 +1,101 @@
; RUN: opt -instcombine < %s
target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
target triple = "powerpc64-unknown-linux-gnu"
%struct.S0.0.1.2.3.4.13.22.31.44.48.53.54.55.56.58.59.60.66.68.70.74.77.106.107.108.109.110.113.117.118.128.129 = type <{ i64 }>
; Function Attrs: nounwind
define void @main() #0 {
entry:
%l_819.i.i = alloca %struct.S0.0.1.2.3.4.13.22.31.44.48.53.54.55.56.58.59.60.66.68.70.74.77.106.107.108.109.110.113.117.118.128.129, align 8
br i1 undef, label %land.lhs.true, label %for.cond.i
land.lhs.true: ; preds = %entry
br label %for.cond.i
for.cond.i: ; preds = %land.lhs.true, %entry
%0 = getelementptr inbounds %struct.S0.0.1.2.3.4.13.22.31.44.48.53.54.55.56.58.59.60.66.68.70.74.77.106.107.108.109.110.113.117.118.128.129* %l_819.i.i, i64 0, i32 0
br label %for.cond.i6.i.i
for.cond.i6.i.i: ; preds = %for.body.i8.i.i, %for.cond.i
br i1 undef, label %for.body.i8.i.i, label %lbl_707.i.i.i
for.body.i8.i.i: ; preds = %for.cond.i6.i.i
br label %for.cond.i6.i.i
lbl_707.i.i.i: ; preds = %for.cond.i6.i.i
br i1 undef, label %lor.rhs.i.i.i, label %lor.end.i.i.i
lor.rhs.i.i.i: ; preds = %lbl_707.i.i.i
br label %lor.end.i.i.i
lor.end.i.i.i: ; preds = %lor.rhs.i.i.i, %lbl_707.i.i.i
br label %for.cond1.i.i.i.i
for.cond1.i.i.i.i: ; preds = %for.body4.i.i.i.i, %lor.end.i.i.i
br i1 undef, label %for.body4.i.i.i.i, label %func_39.exit.i.i
for.body4.i.i.i.i: ; preds = %for.cond1.i.i.i.i
br label %for.cond1.i.i.i.i
func_39.exit.i.i: ; preds = %for.cond1.i.i.i.i
%l_8191.sroa.0.0.copyload.i.i = load i64* %0, align 1
br label %for.cond1.i.i.i
for.cond1.i.i.i: ; preds = %safe_div_func_uint32_t_u_u.exit.i.i.i, %func_39.exit.i.i
br i1 undef, label %for.cond7.i.i.i, label %func_11.exit.i
for.cond7.i.i.i: ; preds = %for.end30.i.i.i, %for.cond1.i.i.i
%storemerge.i.i.i = phi i32 [ %sub.i.i.i, %for.end30.i.i.i ], [ 4, %for.cond1.i.i.i ]
br i1 undef, label %for.cond22.i.i.i, label %for.end32.i.i.i
for.cond22.i.i.i: ; preds = %for.body25.i.i.i, %for.cond7.i.i.i
br i1 undef, label %for.body25.i.i.i, label %for.end30.i.i.i
for.body25.i.i.i: ; preds = %for.cond22.i.i.i
br label %for.cond22.i.i.i
for.end30.i.i.i: ; preds = %for.cond22.i.i.i
%sub.i.i.i = add nsw i32 0, -1
br label %for.cond7.i.i.i
for.end32.i.i.i: ; preds = %for.cond7.i.i.i
%conv33.i.i.i = trunc i64 %l_8191.sroa.0.0.copyload.i.i to i32
%xor.i.i.i.i = xor i32 %storemerge.i.i.i, -701565022
%sub.i.i.i.i = sub nsw i32 0, %storemerge.i.i.i
%xor3.i.i.i.i = xor i32 %sub.i.i.i.i, %storemerge.i.i.i
%and4.i.i.i.i = and i32 %xor.i.i.i.i, %xor3.i.i.i.i
%cmp.i.i.i.i = icmp slt i32 %and4.i.i.i.i, 0
%sub5.i.i.i.i = sub nsw i32 -701565022, %storemerge.i.i.i
%.sub5.i.i.i.i = select i1 %cmp.i.i.i.i, i32 -701565022, i32 %sub5.i.i.i.i
br i1 undef, label %safe_div_func_uint32_t_u_u.exit.i.i.i, label %cond.false.i.i.i.i
cond.false.i.i.i.i: ; preds = %for.end32.i.i.i
%div.i.i.i.i = udiv i32 %conv33.i.i.i, %.sub5.i.i.i.i
br label %safe_div_func_uint32_t_u_u.exit.i.i.i
safe_div_func_uint32_t_u_u.exit.i.i.i: ; preds = %cond.false.i.i.i.i, %for.end32.i.i.i
%cond.i.i.i.i = phi i32 [ %div.i.i.i.i, %cond.false.i.i.i.i ], [ %conv33.i.i.i, %for.end32.i.i.i ]
%cmp35.i.i.i = icmp ne i32 %cond.i.i.i.i, -7
br label %for.cond1.i.i.i
func_11.exit.i: ; preds = %for.cond1.i.i.i
br i1 undef, label %for.body, label %for.end
for.body: ; preds = %func_11.exit.i
unreachable
for.end: ; preds = %func_11.exit.i
br label %for.cond15
for.cond15: ; preds = %for.cond19, %for.end
br i1 undef, label %for.cond19, label %for.end45
for.cond19: ; preds = %for.cond15
br label %for.cond15
for.end45: ; preds = %for.cond15
unreachable
}
attributes #0 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf"="true" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }