https://llvm.org/bugs/show_bug.cgi?id=25864
Bug ID: 25864
Summary: Divergence Analysis: Constant load in branch
considered divergent
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: Global Analyses
Assignee: unassignedb...@nondot.org
Reporter: tstel...@gmail.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 15479
--> https://llvm.org/bugs/attachment.cgi?id=15479&action=edit
Test case
I've run into this issue with the DivergenceAnalysis pass, and I'm not sure if
it is a bug or if it is expected behavior. Attached is the test case, which
can be reproduced by applying this patch: http://reviews.llvm.org/D15608
opt -analyze -divergence -mtriple=amdgcn-- divergent-test.ll
The output I get from the divergence analysis pass is this:
DIVERGENT: float %arg1
DIVERGENT: %tmp2 = fcmp ueq float %arg1, 0.000000e+00
DIVERGENT: br i1 %tmp2, label %bb7, label %bb3
DIVERGENT: %tmp4 = phi i1 [ false, %bb7 ], [ true, %bb ]
DIVERGENT: br i1 %tmp4, label %bb5, label %bb9
DIVERGENT: %tmp6 = call float @llvm.SI.load.const(<16 x i8> %tmp, i32 16)
^ This last line is what I think it incorrect. This is a constant load
intrinsic, which takes a non-divergent argument, so it shouldn't be divergent.
I have verified that AMDGPU's implementation of
TargetTransformInfo::isSourceOfDivergence() returns false for this intrinsic.
Based on brief debugging of the issue I think the problem may be that the
DivergenceAnalysis pass incorrectly things this test case contains a loop, but
I'm not really sure.
--
You are receiving this mail because:
You are on the CC list for the bug.
_______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
