https://bugs.llvm.org/show_bug.cgi?id=38935
Bug ID: 38935
Summary: [LoopAccessAnalysis / IndVarSimplify]
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Global Analyses
Assignee: unassignedb...@nondot.org
Reporter: pauls...@linux.vnet.ibm.com
CC: llvm-bugs@lists.llvm.org
Created attachment 20876
--> https://bugs.llvm.org/attachment.cgi?id=20876&action=edit
reduced testcase
The reduced test case gets its loop vectorized on x86 (icelake-server),while on
SystemZ (z14), this fails (actually in the reduced test case VF 1 is selected,
but the point is that it is *possible* for only one of the targets).
On SystemZ, the IV is rewritten from i32 to i64, which seems to somehow result
in 'LAA: SCEV could not compute the loop exit count.'
It seems like a bug somewhere that when IndVarSimplify makes a transformation,
the SCEV becomes uncomputable.
Could this be something in ScalarEvolution to fix, perhaps?
opt tc_indvar_vec.ll -mtriple=i686-unknown-linux-gnu -mcpu=icelake-server -S -o
/dev/null -O3 -debug-only=loop-accesses |& grep "exit count"
opt tc_indvar_vec.ll -mtriple=systemz-unknown -mcpu=z14 -S -o /dev/null -O3
-debug-only=loop-accesses |& grep "exit count"
LAA: SCEV could not compute the loop exit count.
LAA: SCEV could not compute the loop exit count.
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