[WorkSpanAnalysis] Fix loop-cost analysis to properly evalaute the co…

…st of nested parallel loops with known loop-trip counts.
OpenCilk · Aug 25, 2024 · 976f8b2 · 976f8b2
1 parent 9f5b60a
commit 976f8b2
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Showing 2 changed files with 113 additions and 8 deletions.
diff --git a/llvm/lib/Analysis/WorkSpanAnalysis.cpp b/llvm/lib/Analysis/WorkSpanAnalysis.cpp
@@ -13,20 +13,14 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/WorkSpanAnalysis.h"
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallVector.h"
 #include "llvm/Analysis/CodeMetrics.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/ProfileSummaryInfo.h"
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
-#include "llvm/IR/InstVisitor.h"
-#include "llvm/Support/BranchProbability.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/InstructionCost.h"
 
 using namespace llvm;
 
@@ -74,7 +68,7 @@ static void estimateLoopCostHelper(const Loop *L, CodeMetrics &Metrics,
     }
 
     // Check if the total size of this subloop is huge.
-    if (InstructionCost::getMax() / ConstTripCount > SubLoopCost.Work)
+    if (InstructionCost::getMax() / ConstTripCount < SubLoopCost.Work)
       LoopCost.Work = InstructionCost::getMax();
 
     // Check if this subloop suffices to make loop L huge.

diff --git a/llvm/test/Transforms/Tapir/loop-stripmine-nested-loop.ll b/llvm/test/Transforms/Tapir/loop-stripmine-nested-loop.ll
@@ -0,0 +1,111 @@
+; Check that loop stripmining properly analyzes cost of inner serial loop.
+;
+; RUN: opt < %s -passes="loop-stripmine" -S | FileCheck %s
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define internal fastcc void @_ZN10benchmarks15cilk_mandelbrot17h1d757ad11ef25f85E(i1 %exitcond.not.i) personality ptr null {
+"_ZN63_$LT$alloc..alloc..Global$u20$as$u20$core..alloc..Allocator$GT$8allocate17h8cffd88cc6b3a5e9E.exit.i":
+  %0 = tail call token @llvm.syncregion.start()
+  br label %bb11.i
+
+bb13.i:                                           ; preds = %bb4.i2
+  ret void
+
+bb11.i:                                           ; preds = %bb4.i2, %"_ZN63_$LT$alloc..alloc..Global$u20$as$u20$core..alloc..Allocator$GT$8allocate17h8cffd88cc6b3a5e9E.exit.i"
+  detach within %0, label %bb3.tf.i.tf.tf.tf, label %bb4.i2
+
+bb3.tf.i.tf.tf.tf:                                ; preds = %bb11.i
+  %tf.i.i = tail call token @llvm.taskframe.create()
+  %1 = tail call token @llvm.syncregion.start()
+  br label %bb11.i.i.i
+
+bb11.i.i.i:                                       ; preds = %bb4.i.i.i, %bb3.tf.i.tf.tf.tf
+  %iter.sroa.0.08.i.i.i = phi i64 [ %_0.i4.i.i.i, %bb4.i.i.i ], [ 0, %bb3.tf.i.tf.tf.tf ]
+  %_0.i4.i.i.i = add i64 %iter.sroa.0.08.i.i.i, 1
+  detach within %1, label %bb3.i.i.i, label %bb4.i.i.i
+
+bb3.i.i.i:                                        ; preds = %bb11.i.i.i
+  br label %bb2.i.i.i.i
+
+bb2.i.i.i.i:                                      ; preds = %bb2.i.i.i.i, %bb3.i.i.i
+  %depth.02.i.i.i.i = phi double [ 0.000000e+00, %bb3.i.i.i ], [ %2, %bb2.i.i.i.i ]
+  %2 = fadd double %depth.02.i.i.i.i, 1.000000e+00
+  %_16.i.i.i.i.1 = fcmp olt double %2, 1.000000e+02
+  br i1 %_16.i.i.i.i.1, label %bb2.i.i.i.i, label %"_ZN10benchmarks15cilk_mandelbrot28_$u7b$$u7b$closure$u7d$$u7d$28_$u7b$$u7b$closure$u7d$$u7d$17h37d21dcab212431cE.exit.i.i.i"
+
+"_ZN10benchmarks15cilk_mandelbrot28_$u7b$$u7b$closure$u7d$$u7d$28_$u7b$$u7b$closure$u7d$$u7d$17h37d21dcab212431cE.exit.i.i.i": ; preds = %bb2.i.i.i.i
+  reattach within %1, label %bb4.i.i.i
+
+bb4.i.i.i:                                        ; preds = %"_ZN10benchmarks15cilk_mandelbrot28_$u7b$$u7b$closure$u7d$$u7d$28_$u7b$$u7b$closure$u7d$$u7d$17h37d21dcab212431cE.exit.i.i.i", %bb11.i.i.i
+  %exitcond.not.i.i.i = icmp eq i64 %iter.sroa.0.08.i.i.i, 20480
+  br i1 %exitcond.not.i.i.i, label %"_ZN10benchmarks15cilk_mandelbrot28_$u7b$$u7b$closure$u7d$$u7d$17h9b0c8d58900499abE.exit.i.tfend", label %bb11.i.i.i, !llvm.loop !0
+
+"_ZN10benchmarks15cilk_mandelbrot28_$u7b$$u7b$closure$u7d$$u7d$17h9b0c8d58900499abE.exit.i.tfend": ; preds = %bb4.i.i.i
+  tail call void @llvm.taskframe.end(token %tf.i.i)
+  reattach within %0, label %bb4.i2
+
+bb4.i2:                                           ; preds = %"_ZN10benchmarks15cilk_mandelbrot28_$u7b$$u7b$closure$u7d$$u7d$17h9b0c8d58900499abE.exit.i.tfend", %bb11.i
+  br i1 %exitcond.not.i, label %bb13.i, label %bb11.i
+}
+
+; CHECK: define internal fastcc void @_ZN10benchmarks15cilk_mandelbrot17h1d757ad11ef25f85E(
+; CHECK: detach within %[[OUTER_SYNCREG:.+]], label %{{.+}}, label %{{.+}}
+; CHECK: %[[TF_I:.+]] = {{.*}}call token @llvm.taskframe.create()
+; CHECK: detach within %[[INNER_SYNCREG:.+]], label %{{.+}}, label %{{.+}}
+
+; CHECK: detach within %[[STRPM_DETACHLOOP:.+]], label %[[STRPM_OUTER:.+]], label %{{.+}}
+
+; CHECK: [[STRPM_OUTER]]:
+; CHECK-NEXT: mul
+; CHECK-NEXT: br label %[[INNER_SERIAL_LOOP:.+]]
+
+; CHECK: [[INNER_SERIAL_LOOP]]:
+; CHECK-NEXT: phi
+; CHECK: br label %[[WHILE_LOOP_PH:.+]]
+
+; CHECK: [[WHILE_LOOP_PH]]:
+; CHECK: br label %[[WHILE_HEADER:.+]]
+
+; CHECK: [[WHILE_HEADER]]:
+; CHECK-NEXT: phi
+
+; CHECK: br i1 %{{.+}}, label %[[WHILE_HEADER]], label %[[WHILE_EXIT:.+]]
+
+; CHECK: [[WHILE_EXIT]]:
+; CHECK: br i1 %{{.+}}, label %[[INNER_SERIAL_LOOP_REATTACH:.+]], label %[[INNER_SERIAL_LOOP]]
+
+; CHECK: [[INNER_SERIAL_LOOP_REATTACH]]:
+; CHECK-NEXT: reattach within %[[STRPM_DETACHLOOP]], label %[[STRPM_LATCH:.+]]
+
+; CHECK: [[STRPM_LATCH]]:
+; CHECK: br i1 %{{.+}}, label %{{.+}}, label %{{.+}}, !llvm.loop ![[STRPM_LOOPMD:.+]]
+
+; CHECK: sync within %[[STRPM_DETACHLOOP]], label %{{.+}}
+; CHECK: reattach within %[[INNER_SYNCREG]]
+; CHECK: call void @llvm.taskframe.end(token %[[TF_I]]
+; CHECK: reattach within %[[OUTER_SYNCREG]], label %[[LATCH:.+]]
+
+; CHECK: [[LATCH]]:
+; CHECK: br i1 %{{.+}}, label %{{.+}}, label %{{.+}}, !llvm.loop ![[LOOPMD:.+]]
+
+; CHECK: ![[STRPM_LOOPMD]] = distinct !{![[STRPM_LOOPMD]], !{{[0-9]+}}, ![[GRANSIZEMD:[0-9]+]]}
+; CHECK: ![[GRANSIZEMD]] = !{!"tapir.loop.grainsize", i32 1}
+
+; Function Attrs: nounwind willreturn memory(argmem: readwrite)
+declare token @llvm.syncregion.start() #0
+
+; Function Attrs: nounwind willreturn memory(argmem: readwrite)
+declare token @llvm.taskframe.create() #0
+
+; Function Attrs: nounwind willreturn memory(argmem: readwrite)
+declare void @llvm.taskframe.end(token) #0
+
+; uselistorder directives
+uselistorder ptr null, { 1, 2, 0 }
+uselistorder ptr @llvm.syncregion.start, { 1, 0 }
+
+attributes #0 = { nounwind willreturn memory(argmem: readwrite) }
+
+!0 = distinct !{!0, !1}
+!1 = !{!"tapir.loop.spawn.strategy", i32 1}