Improve vectorization diagnostic messages and extend vectorize(enable) pragma.
This patch changes the analysis diagnostics produced when loops with floating-point recurrences or memory operations are identified. The new messages say "cannot prove it is safe to reorder * operations; allow reordering by specifying #pragma clang loop vectorize(enable)". Depending on the type of diagnostic the message will include additional options such as ffast-math or __restrict__. This patch also allows the vectorize(enable) pragma to override the low pointer memory check threshold. When the hint is given a higher threshold is used. See the clang patch for the options produced for each diagnostic. llvm-svn: 246187
This commit is contained in:
Tyler Nowicki
parent
05845d31c9
commit
5eaa5a9d26
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@ -214,6 +214,11 @@ static cl::opt<unsigned> MaxNestedScalarReductionIC(
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cl::desc("The maximum interleave count to use when interleaving a scalar "
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"reduction in a nested loop."));
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static cl::opt<unsigned> PragmaVectorizeMemoryCheckThreshold(
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"pragma-vectorize-memory-check-threshold", cl::init(128), cl::Hidden,
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cl::desc("The maximum allowed number of runtime memory checks with a "
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"vectorize(enable) pragma."));
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namespace {
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// Forward declarations.
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@ -929,6 +934,15 @@ public:
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return DiagnosticInfo::AlwaysPrint;
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}
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bool allowReordering() const {
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// When enabling loop hints are provided we allow the vectorizer to change
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// the order of operations that is given by the scalar loop. This is not
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// enabled by default because can be unsafe or inefficient. For example,
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// reordering floating-point operations will change the way round-off
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// error accumulates in the loop.
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return getForce() == LoopVectorizeHints::FK_Enabled || getWidth() > 1;
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}
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private:
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/// Find hints specified in the loop metadata and update local values.
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void getHintsFromMetadata() {
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@ -1427,29 +1441,25 @@ public:
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bool doesNotMeet(Function *F, Loop *L, const LoopVectorizeHints &Hints) {
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const char *Name = Hints.vectorizeAnalysisPassName();
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bool Failed = false;
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if (UnsafeAlgebraInst &&
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Hints.getForce() == LoopVectorizeHints::FK_Undefined &&
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Hints.getWidth() == 0) {
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if (UnsafeAlgebraInst && !Hints.allowReordering()) {
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emitOptimizationRemarkAnalysisFPCommute(
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F->getContext(), Name, *F, UnsafeAlgebraInst->getDebugLoc(),
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VectorizationReport() << "vectorization requires changes in the "
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"order of operations, however IEEE 754 "
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"floating-point operations are not "
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"commutative");
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VectorizationReport() << "cannot prove it is safe to reorder "
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"floating-point operations");
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Failed = true;
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}
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if (NumRuntimePointerChecks >
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VectorizerParams::RuntimeMemoryCheckThreshold) {
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// Test if runtime memcheck thresholds are exceeded.
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bool PragmaThresholdReached =
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NumRuntimePointerChecks > PragmaVectorizeMemoryCheckThreshold;
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bool ThresholdReached =
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NumRuntimePointerChecks > VectorizerParams::RuntimeMemoryCheckThreshold;
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if ((ThresholdReached && !Hints.allowReordering()) ||
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PragmaThresholdReached) {
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emitOptimizationRemarkAnalysisAliasing(
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F->getContext(), Name, *F, L->getStartLoc(),
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VectorizationReport()
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<< "cannot prove pointers refer to independent arrays in memory. "
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"The loop requires "
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<< NumRuntimePointerChecks
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<< " runtime independence checks to vectorize the loop, but that "
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"would exceed the limit of "
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<< VectorizerParams::RuntimeMemoryCheckThreshold << " checks");
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<< "cannot prove it is safe to reorder memory operations");
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DEBUG(dbgs() << "LV: Too many memory checks needed.\n");
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Failed = true;
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}
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@ -1,6 +1,6 @@
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; RUN: opt < %s -loop-vectorize -mtriple=x86_64-unknown-linux -S -pass-remarks='loop-vectorize' -pass-remarks-missed='loop-vectorize' -pass-remarks-analysis='loop-vectorize' 2>&1 | FileCheck %s
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; CHECK: remark: no_fpmath.c:6:11: loop not vectorized: vectorization requires changes in the order of operations, however IEEE 754 floating-point operations are not commutative
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; CHECK: remark: no_fpmath.c:6:11: loop not vectorized: cannot prove it is safe to reorder floating-point operations
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; CHECK: remark: no_fpmath.c:6:14: loop not vectorized:
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; CHECK: remark: no_fpmath.c:17:14: vectorized loop (vectorization width: 2, interleaved count: 2)
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@ -1,17 +1,27 @@
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; RUN: opt < %s -loop-vectorize -force-vector-interleave=1 -force-vector-width=4 -dce -instcombine -pass-remarks=loop-vectorize -pass-remarks-missed=loop-vectorize -S 2>&1 | FileCheck %s
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; RUN: opt < %s -loop-vectorize -force-vector-interleave=1 -dce -instcombine -pass-remarks=loop-vectorize -pass-remarks-missed=loop-vectorize -S 2>&1 | FileCheck %s
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; RUN: opt < %s -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 -dce -instcombine -pass-remarks=loop-vectorize -pass-remarks-missed=loop-vectorize -S 2>&1 | FileCheck %s -check-prefix=OVERRIDE
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; RUN: opt < %s -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 -pragma-vectorize-memory-check-threshold=6 -dce -instcombine -pass-remarks=loop-vectorize -pass-remarks-missed=loop-vectorize -S 2>&1 | FileCheck %s
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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-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
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target triple = "x86_64-apple-macosx10.8.0"
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; First loop produced diagnostic pass remark.
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;CHECK: remark: {{.*}}:0:0: vectorized loop (vectorization width: 4, interleaved count: 1)
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;CHECK: remark: {{.*}}:0:0: vectorized loop (vectorization width: {{[0-9]}}, interleaved count: 1)
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; Second loop produces diagnostic analysis remark.
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;CHECK: remark: {{.*}}:0:0: loop not vectorized: cannot prove pointers refer to independent arrays in memory. The loop requires 11 runtime independence checks to vectorize the loop, but that would exceed the limit of 8 checks
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;CHECK: remark: {{.*}}:0:0: loop not vectorized: cannot prove it is safe to reorder memory operations
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; First loop produced diagnostic pass remark.
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;OVERRIDE: remark: {{.*}}:0:0: vectorized loop (vectorization width: {{[0-9]}}, interleaved count: 1)
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; Second loop produces diagnostic pass remark.
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;OVERRIDE: remark: {{.*}}:0:0: vectorized loop (vectorization width: {{[0-9]}}, interleaved count: 1)
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; We are vectorizing with 6 runtime checks.
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;CHECK-LABEL: func1x6(
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;CHECK: <4 x i32>
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;CHECK: <{{[0-9]}} x i32>
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;CHECK: ret
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;OVERRIDE-LABEL: func1x6(
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;OVERRIDE: <4 x i32>
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;OVERRIDE: ret
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define i32 @func1x6(i32* nocapture %out, i32* nocapture %A, i32* nocapture %B, i32* nocapture %C, i32* nocapture %D, i32* nocapture %E, i32* nocapture %F) {
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entry:
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br label %for.body
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@ -44,8 +54,12 @@ for.end: ; preds = %for.body
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; We are not vectorizing with 12 runtime checks.
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;CHECK-LABEL: func2x6(
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;CHECK-NOT: <4 x i32>
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;CHECK-NOT: <{{[0-9]}} x i32>
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;CHECK: ret
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; We vectorize with 12 checks if a vectorization hint is provided.
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;OVERRIDE-LABEL: func2x6(
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;OVERRIDE: <4 x i32>
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;OVERRIDE: ret
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define i32 @func2x6(i32* nocapture %out, i32* nocapture %out2, i32* nocapture %A, i32* nocapture %B, i32* nocapture %C, i32* nocapture %D, i32* nocapture %E, i32* nocapture %F) {
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entry:
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br label %for.body
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