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llvm-project/polly/test/ScopInfo/assume_gep_bounds_2.ll

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[ScopInfo] Simplify inbounds assumptions under domain constraints Without this simplification for a loop nest: void foo(long n1_a, long n1_b, long n1_c, long n1_d, long p1_b, long p1_c, long p1_d, float A_1[][p1_b][p1_c][p1_d]) { for (long i = 0; i < n1_a; i++) for (long j = 0; j < n1_b; j++) for (long k = 0; k < n1_c; k++) for (long l = 0; l < n1_d; l++) A_1[i][j][k][l] += i + j + k + l; } the assumption: n1_a <= 0 or (n1_a > 0 and n1_b <= 0) or (n1_a > 0 and n1_b > 0 and n1_c <= 0) or (n1_a > 0 and n1_b > 0 and n1_c > 0 and n1_d <= 0) or (n1_a > 0 and n1_b > 0 and n1_c > 0 and n1_d > 0 and p1_b >= n1_b and p1_c >= n1_c and p1_d >= n1_d) is taken rather than the simpler assumption: p9_b >= n9_b and p9_c >= n9_c and p9_d >= n9_d. The former is less strict, as it allows arbitrary values of p1_* in case, the loop is not executed at all. However, in practice these precise constraints explode when combined across different accesses and loops. For now it seems to make more sense to take less precise, but more scalable constraints by default. In case we find a practical example where more precise constraints are needed, we can think about allowing such precise constraints in specific situations where they help. This change speeds up the new test case from taking very long (waited at least a minute, but it probably takes a lot more) to below a second. llvm-svn: 296456
2017-02-28 17:45:54 +08:00
; RUN: opt %loadPolly -basicaa -polly-scops -analyze < %s \
; RUN: -polly-precise-inbounds | FileCheck %s
Assume GetElementPtr offsets to be inbounds In case a GEP instruction references into a fixed size array e.g., an access A[i][j] into an array A[100x100], LLVM-IR does not guarantee that the subscripts always compute values that are within array bounds. We now derive the set of parameter values for which all accesses are within bounds and add the assumption that the scop is only every executed with this set of parameter values. Example: void foo(float A[][20], long n, long m { for (long i = 0; i < n; i++) for (long j = 0; j < m; j++) A[i][j] = ... This loop yields out-of-bound accesses if m is at least 20 and at the same time at least one iteration of the outer loop is executed. Hence, we assume: n <= 0 or m <= 20. Doing so simplifies the dependence analysis problem, allows us to perform more optimizations and generate better code. TODO: The location where the GEP instruction is executed is not necessarily the location where the memory is actually accessed. As a result scanning for GEP[s] is imprecise. Even though this is not a correctness problem, this imprecision may result in missed optimizations or non-optimal run-time checks. In polybench where this mismatch between parametric loop bounds and fixed size arrays is common, we see with this patch significant reductions in compile time (up to 50%) and execution time (up to 70%). We see two significant compile time regressions (fdtd-2d, jacobi-2d-imper), and one execution time regression (trmm). Both regressions arise due to additional optimizations that have been enabled by this patch. They can be addressed in subsequent commits. http://reviews.llvm.org/D6369 llvm-svn: 222754
2014-11-25 18:51:12 +08:00
;
; void foo(float A[restrict][20], float B[restrict][20], long n, long m,
; long p) {
; for (long i = 0; i < n; i++)
; for (long j = 0; j < m; j++)
; A[i][j] = i + j;
; for (long i = 0; i < m; i++)
; for (long j = 0; j < p; j++)
; B[i][j] = i + j;
; }
; This code is within bounds either if m and p are smaller than the array sizes,
; but also if only p is smaller than the size of the second B dimension and n
; is such that the first loop is never executed and consequently A is never
; accessed. In this case the value of m does not matter.
Prepare unit tests for update to ISL 0.16 ISL 0.16 will change how sets are printed which breaks 117 unit tests that text-compare printed sets. This patch re-formats most of these unit tests using a script and small manual editing on top of that. When actually updating ISL, most work is done by just re-running the script to adapt to the changed output. Some tests that compare IR and tests with single CHECK-lines that can be easily updated manually are not included here. The re-format script will also be committed afterwards. The per-test formatter invocation command lines options will not be added in the near future because it is ad hoc and would overwrite the manual edits. Ideally it also shouldn't be required anymore because ISL's set printing has become more stable in 0.16. Differential Revision: http://reviews.llvm.org/D16095 llvm-svn: 257851
2016-01-15 08:48:42 +08:00
; CHECK: Assumed Context:
Update to ISL 0.16.1 llvm-svn: 257898
2016-01-15 23:54:45 +08:00
; CHECK-NEXT: [n, m, p] -> { : p <= 20 and (n <= 0 or (n > 0 and m <= 20)) }
Assume GetElementPtr offsets to be inbounds In case a GEP instruction references into a fixed size array e.g., an access A[i][j] into an array A[100x100], LLVM-IR does not guarantee that the subscripts always compute values that are within array bounds. We now derive the set of parameter values for which all accesses are within bounds and add the assumption that the scop is only every executed with this set of parameter values. Example: void foo(float A[][20], long n, long m { for (long i = 0; i < n; i++) for (long j = 0; j < m; j++) A[i][j] = ... This loop yields out-of-bound accesses if m is at least 20 and at the same time at least one iteration of the outer loop is executed. Hence, we assume: n <= 0 or m <= 20. Doing so simplifies the dependence analysis problem, allows us to perform more optimizations and generate better code. TODO: The location where the GEP instruction is executed is not necessarily the location where the memory is actually accessed. As a result scanning for GEP[s] is imprecise. Even though this is not a correctness problem, this imprecision may result in missed optimizations or non-optimal run-time checks. In polybench where this mismatch between parametric loop bounds and fixed size arrays is common, we see with this patch significant reductions in compile time (up to 50%) and execution time (up to 70%). We see two significant compile time regressions (fdtd-2d, jacobi-2d-imper), and one execution time regression (trmm). Both regressions arise due to additional optimizations that have been enabled by this patch. They can be addressed in subsequent commits. http://reviews.llvm.org/D6369 llvm-svn: 222754
2014-11-25 18:51:12 +08:00
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
define void @foo([20 x float]* noalias %A, [20 x float]* noalias %B, i64 %n, i64 %m, i64 %p) {
entry:
br label %for.cond
for.cond: ; preds = %for.inc5, %entry
%i.0 = phi i64 [ 0, %entry ], [ %inc6, %for.inc5 ]
%cmp = icmp slt i64 %i.0, %n
br i1 %cmp, label %for.body, label %for.end7
for.body: ; preds = %for.cond
br label %for.cond1
for.cond1: ; preds = %for.inc, %for.body
%j.0 = phi i64 [ 0, %for.body ], [ %inc, %for.inc ]
%cmp2 = icmp slt i64 %j.0, %m
br i1 %cmp2, label %for.body3, label %for.end
for.body3: ; preds = %for.cond1
%add = add nsw i64 %i.0, %j.0
%conv = sitofp i64 %add to float
Update Polly tests to handle explicitly typed gep changes in LLVM llvm-svn: 230784
2015-02-28 03:20:19 +08:00
%arrayidx4 = getelementptr inbounds [20 x float], [20 x float]* %A, i64 %i.0, i64 %j.0
Assume GetElementPtr offsets to be inbounds In case a GEP instruction references into a fixed size array e.g., an access A[i][j] into an array A[100x100], LLVM-IR does not guarantee that the subscripts always compute values that are within array bounds. We now derive the set of parameter values for which all accesses are within bounds and add the assumption that the scop is only every executed with this set of parameter values. Example: void foo(float A[][20], long n, long m { for (long i = 0; i < n; i++) for (long j = 0; j < m; j++) A[i][j] = ... This loop yields out-of-bound accesses if m is at least 20 and at the same time at least one iteration of the outer loop is executed. Hence, we assume: n <= 0 or m <= 20. Doing so simplifies the dependence analysis problem, allows us to perform more optimizations and generate better code. TODO: The location where the GEP instruction is executed is not necessarily the location where the memory is actually accessed. As a result scanning for GEP[s] is imprecise. Even though this is not a correctness problem, this imprecision may result in missed optimizations or non-optimal run-time checks. In polybench where this mismatch between parametric loop bounds and fixed size arrays is common, we see with this patch significant reductions in compile time (up to 50%) and execution time (up to 70%). We see two significant compile time regressions (fdtd-2d, jacobi-2d-imper), and one execution time regression (trmm). Both regressions arise due to additional optimizations that have been enabled by this patch. They can be addressed in subsequent commits. http://reviews.llvm.org/D6369 llvm-svn: 222754
2014-11-25 18:51:12 +08:00
store float %conv, float* %arrayidx4, align 4
br label %for.inc
for.inc: ; preds = %for.body3
%inc = add nsw i64 %j.0, 1
br label %for.cond1
for.end: ; preds = %for.cond1
br label %for.inc5
for.inc5: ; preds = %for.end
%inc6 = add nsw i64 %i.0, 1
br label %for.cond
for.end7: ; preds = %for.cond
br label %for.cond9
for.cond9: ; preds = %for.inc25, %for.end7
%i8.0 = phi i64 [ 0, %for.end7 ], [ %inc26, %for.inc25 ]
%cmp10 = icmp slt i64 %i8.0, %m
br i1 %cmp10, label %for.body12, label %for.end27
for.body12: ; preds = %for.cond9
br label %for.cond14
for.cond14: ; preds = %for.inc22, %for.body12
%j13.0 = phi i64 [ 0, %for.body12 ], [ %inc23, %for.inc22 ]
%cmp15 = icmp slt i64 %j13.0, %p
br i1 %cmp15, label %for.body17, label %for.end24
for.body17: ; preds = %for.cond14
%add18 = add nsw i64 %i8.0, %j13.0
%conv19 = sitofp i64 %add18 to float
Update Polly tests to handle explicitly typed gep changes in LLVM llvm-svn: 230784
2015-02-28 03:20:19 +08:00
%arrayidx21 = getelementptr inbounds [20 x float], [20 x float]* %B, i64 %i8.0, i64 %j13.0
Assume GetElementPtr offsets to be inbounds In case a GEP instruction references into a fixed size array e.g., an access A[i][j] into an array A[100x100], LLVM-IR does not guarantee that the subscripts always compute values that are within array bounds. We now derive the set of parameter values for which all accesses are within bounds and add the assumption that the scop is only every executed with this set of parameter values. Example: void foo(float A[][20], long n, long m { for (long i = 0; i < n; i++) for (long j = 0; j < m; j++) A[i][j] = ... This loop yields out-of-bound accesses if m is at least 20 and at the same time at least one iteration of the outer loop is executed. Hence, we assume: n <= 0 or m <= 20. Doing so simplifies the dependence analysis problem, allows us to perform more optimizations and generate better code. TODO: The location where the GEP instruction is executed is not necessarily the location where the memory is actually accessed. As a result scanning for GEP[s] is imprecise. Even though this is not a correctness problem, this imprecision may result in missed optimizations or non-optimal run-time checks. In polybench where this mismatch between parametric loop bounds and fixed size arrays is common, we see with this patch significant reductions in compile time (up to 50%) and execution time (up to 70%). We see two significant compile time regressions (fdtd-2d, jacobi-2d-imper), and one execution time regression (trmm). Both regressions arise due to additional optimizations that have been enabled by this patch. They can be addressed in subsequent commits. http://reviews.llvm.org/D6369 llvm-svn: 222754
2014-11-25 18:51:12 +08:00
store float %conv19, float* %arrayidx21, align 4
br label %for.inc22
for.inc22: ; preds = %for.body17
%inc23 = add nsw i64 %j13.0, 1
br label %for.cond14
for.end24: ; preds = %for.cond14
br label %for.inc25
for.inc25: ; preds = %for.end24
%inc26 = add nsw i64 %i8.0, 1
br label %for.cond9
for.end27: ; preds = %for.cond9
ret void
}