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-indvars pass fails to replace exit value of loop when profitable #1551

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lattner opened this issue Feb 5, 2007 · 6 comments
Closed

-indvars pass fails to replace exit value of loop when profitable #1551

lattner opened this issue Feb 5, 2007 · 6 comments
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bugzilla Issues migrated from bugzilla code-quality loopoptim regression

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lattner commented Feb 5, 2007

Bugzilla Link 1179
Resolution FIXED
Resolved on May 05, 2019 06:32
Version 1.8
OS All
CC @nlewycky

Extended Description

The -indvars pass is not computing the exit value of j in either of these cases:

int ltst(int x) {
int i, j;
j=0;
for(i=0; i<x; i++)j++;
return(j);
}

int ltst(int x) {
int i = 0, j = 0
do {
j++, i++;
} while (i < x);
return(j);
}
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lattner commented Feb 5, 2007

assigned to @lattner

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lattner commented Feb 15, 2007

Another obvious case:

int main() {
int i = 0;
for (int x = 0; x < 200000; ++x)
i += 3;
return i;
}

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lattner commented Mar 1, 2007

*** Bug llvm/llvm-bugzilla-archive#1232 has been marked as a duplicate of this bug. ***

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lattner commented Mar 3, 2007

This regression is largely due to LCSSA landing. For example, the input to indvars on the code in
comment #​1 is:

define i32 @​foo() {
entry:
br label %bb5

bb5: ; preds = %bb5, %entry
%x.03.0 = phi i32 [ 0, %entry ], [ %indvar.next, %bb5 ] ; [#uses=2]
%i.01.0 = mul i32 %x.03.0, 3 ; [#uses=1]
%tmp2 = add i32 %i.01.0, 3 ; [#uses=1]
%indvar.next = add i32 %x.03.0, 1 ; [#uses=2]
icmp ne i32 %indvar.next, 200000 ; :0 [#uses=1]
br i1 %0, label %bb5, label %bb7

bb7: ; preds = %bb5
%tmp2.lcssa = phi i32 [ %tmp2, %bb5 ] ; [#uses=1]
ret i32 %tmp2.lcssa
}

the LCSSA phi node prevents exit value substitution due to IndVarSimplify.cpp:347

-Chris

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lattner commented Mar 4, 2007

Implemented. Patch here:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070226/045475.html

Testcases here: test/Transforms/IndVarsSimplify/loop_evaluate_[234].ll

-Chris

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lattner commented Nov 26, 2021

mentioned in issue llvm/llvm-bugzilla-archive#1232

@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 3, 2021
jeanPerier pushed a commit to jeanPerier/llvm-project that referenced this issue Apr 1, 2022
@vdonaldson
system_clock intrinsic calls with dynamically optional arguments (llv…
6a62c62 
…m#1551)

system_clock intrinsic calls with dynamically optional arguments

Modify intrinsic system_clock calls to allow for an argument that is optional
or a disassociated pointer or an unallocated allocatable.  A call with such an
argument is the same as a call that does not specify that argument.

Rename (genIsNotNull -> genIsNotNullAddr) and (genIsNull -> genIsNullAddr)
and add a use of genIsNotNullAddr.
troelsbjerre pushed a commit to troelsbjerre/llvm-project that referenced this issue Jan 10, 2024
@JDevlieghere
Merge pull request llvm#1551 from JDevlieghere/🍒/apple/stable/2020071…
8ef5bf2 
…4/0b339c069266b7a4f3c82f80067d74620cbe19c4

[lldb] Inform every language runtime of the modified modules
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