[llvm] 424d6cb - [SCEV] Compute ranges for lshr recurrences
Philip Reames via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 22 11:06:38 PDT 2021
Author: Philip Reames
Date: 2021-04-22T11:06:31-07:00
New Revision: 424d6cb902e4e05695a92e753a7ffa2fef16e268
URL: https://github.com/llvm/llvm-project/commit/424d6cb902e4e05695a92e753a7ffa2fef16e268
DIFF: https://github.com/llvm/llvm-project/commit/424d6cb902e4e05695a92e753a7ffa2fef16e268.diff
LOG: [SCEV] Compute ranges for lshr recurrences
Straight forward extension to the recently added infrastructure which was pioneered with shl.
Differential Revision: https://reviews.llvm.org/D99687
Added:
Modified:
llvm/lib/Analysis/ScalarEvolution.cpp
llvm/test/Analysis/ScalarEvolution/shift-recurrences.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 498acfe2df85c..43ec432e42344 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -5696,6 +5696,7 @@ getRangeForUnknownRecurrence(const SCEVUnknown *U) {
switch (BO->getOpcode()) {
default:
return CR;
+ case Instruction::LShr:
case Instruction::Shl:
break;
};
@@ -5724,6 +5725,19 @@ getRangeForUnknownRecurrence(const SCEVUnknown *U) {
switch (BO->getOpcode()) {
default:
llvm_unreachable("filtered out above");
+ case Instruction::LShr: {
+ // For each lshr, three cases:
+ // shift = 0 => unchanged value
+ // saturation => 0
+ // other => a smaller positive number
+ // Thus, the low end of the unsigned range is the last value produced.
+ auto KnownEnd = KnownBits::lshr(KnownStart,
+ KnownBits::makeConstant(TotalShift));
+ auto R = ConstantRange::getNonEmpty(KnownEnd.getMinValue(),
+ KnownStart.getMaxValue() + 1);
+ CR = CR.intersectWith(R);
+ break;
+ }
case Instruction::Shl: {
// Iff no bits are shifted out, value increases on every shift.
auto KnownEnd = KnownBits::shl(KnownStart,
diff --git a/llvm/test/Analysis/ScalarEvolution/shift-recurrences.ll b/llvm/test/Analysis/ScalarEvolution/shift-recurrences.ll
index 9c8944fc70122..2ed80c7f0a430 100644
--- a/llvm/test/Analysis/ScalarEvolution/shift-recurrences.ll
+++ b/llvm/test/Analysis/ScalarEvolution/shift-recurrences.ll
@@ -630,11 +630,11 @@ define void @test_lshr_tc_positive() {
; CHECK-NEXT: %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {0,+,1}<%loop> U: [0,5) S: [0,5) Exits: 4 LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.lshr = phi i64 [ 1023, %entry ], [ %iv.lshr.next, %loop ]
-; CHECK-NEXT: --> %iv.lshr U: [0,1024) S: [0,1024) Exits: 63 LoopDispositions: { %loop: Variant }
+; CHECK-NEXT: --> %iv.lshr U: [63,1024) S: [63,1024) Exits: 63 LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %iv.next = add i64 %iv, 1
; CHECK-NEXT: --> {1,+,1}<%loop> U: [1,6) S: [1,6) Exits: 5 LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.lshr.next = lshr i64 %iv.lshr, 1
-; CHECK-NEXT: --> (%iv.lshr /u 2) U: [0,512) S: [0,512) Exits: 31 LoopDispositions: { %loop: Variant }
+; CHECK-NEXT: --> (%iv.lshr /u 2) U: [31,512) S: [31,512) Exits: 31 LoopDispositions: { %loop: Variant }
; CHECK-NEXT: Determining loop execution counts for: @test_lshr_tc_positive
; CHECK-NEXT: Loop %loop: backedge-taken count is 4
; CHECK-NEXT: Loop %loop: max backedge-taken count is 4
@@ -661,11 +661,11 @@ define void @test_lshr_tc_negative() {
; CHECK-NEXT: %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {0,+,1}<%loop> U: [0,5) S: [0,5) Exits: 4 LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.lshr = phi i8 [ -1, %entry ], [ %iv.lshr.next, %loop ]
-; CHECK-NEXT: --> %iv.lshr U: [-1,-128) S: [-1,-128) Exits: 15 LoopDispositions: { %loop: Variant }
+; CHECK-NEXT: --> %iv.lshr U: [15,0) S: [-1,-128) Exits: 15 LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %iv.next = add i64 %iv, 1
; CHECK-NEXT: --> {1,+,1}<%loop> U: [1,6) S: [1,6) Exits: 5 LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.lshr.next = lshr i8 %iv.lshr, 1
-; CHECK-NEXT: --> (%iv.lshr /u 2) U: [0,-128) S: [0,-128) Exits: 7 LoopDispositions: { %loop: Variant }
+; CHECK-NEXT: --> (%iv.lshr /u 2) U: [7,-128) S: [7,-128) Exits: 7 LoopDispositions: { %loop: Variant }
; CHECK-NEXT: Determining loop execution counts for: @test_lshr_tc_negative
; CHECK-NEXT: Loop %loop: backedge-taken count is 4
; CHECK-NEXT: Loop %loop: max backedge-taken count is 4
@@ -726,11 +726,11 @@ define void @test_lshr_zero_shift() {
; CHECK-NEXT: %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {0,+,1}<%loop> U: [0,5) S: [0,5) Exits: 4 LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.lshr = phi i64 [ 1023, %entry ], [ %iv.lshr.next, %loop ]
-; CHECK-NEXT: --> %iv.lshr U: [0,1024) S: [0,1024) Exits: 1023 LoopDispositions: { %loop: Variant }
+; CHECK-NEXT: --> %iv.lshr U: [1023,1024) S: [1023,1024) Exits: 1023 LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %iv.next = add i64 %iv, 1
; CHECK-NEXT: --> {1,+,1}<%loop> U: [1,6) S: [1,6) Exits: 5 LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.lshr.next = lshr i64 %iv.lshr, 0
-; CHECK-NEXT: --> %iv.lshr U: [0,1024) S: [0,1024) Exits: 1023 LoopDispositions: { %loop: Variant }
+; CHECK-NEXT: --> %iv.lshr U: [1023,1024) S: [1023,1024) Exits: 1023 LoopDispositions: { %loop: Variant }
; CHECK-NEXT: Determining loop execution counts for: @test_lshr_zero_shift
; CHECK-NEXT: Loop %loop: backedge-taken count is 4
; CHECK-NEXT: Loop %loop: max backedge-taken count is 4
@@ -758,11 +758,11 @@ define void @test_lshr_power_of_2_start() {
; CHECK-NEXT: %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {0,+,1}<%loop> U: [0,5) S: [0,5) Exits: 4 LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.lshr = phi i64 [ 1024, %entry ], [ %iv.lshr.next, %loop ]
-; CHECK-NEXT: --> %iv.lshr U: [0,1025) S: [0,1025) Exits: 4 LoopDispositions: { %loop: Variant }
+; CHECK-NEXT: --> %iv.lshr U: [4,1025) S: [4,1025) Exits: 4 LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %iv.next = add i64 %iv, 1
; CHECK-NEXT: --> {1,+,1}<%loop> U: [1,6) S: [1,6) Exits: 5 LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.lshr.next = lshr i64 %iv.lshr, 2
-; CHECK-NEXT: --> (%iv.lshr /u 4) U: [0,512) S: [0,512) Exits: 1 LoopDispositions: { %loop: Variant }
+; CHECK-NEXT: --> (%iv.lshr /u 4) U: [1,257) S: [1,257) Exits: 1 LoopDispositions: { %loop: Variant }
; CHECK-NEXT: Determining loop execution counts for: @test_lshr_power_of_2_start
; CHECK-NEXT: Loop %loop: backedge-taken count is 4
; CHECK-NEXT: Loop %loop: max backedge-taken count is 4
@@ -790,11 +790,11 @@ define void @test_lshr_arbitrary_start() {
; CHECK-NEXT: %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {0,+,1}<%loop> U: [0,5) S: [0,5) Exits: 4 LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.lshr = phi i64 [ 957, %entry ], [ %iv.lshr.next, %loop ]
-; CHECK-NEXT: --> %iv.lshr U: [0,958) S: [0,958) Exits: 3 LoopDispositions: { %loop: Variant }
+; CHECK-NEXT: --> %iv.lshr U: [3,958) S: [3,958) Exits: 3 LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %iv.next = add i64 %iv, 1
; CHECK-NEXT: --> {1,+,1}<%loop> U: [1,6) S: [1,6) Exits: 5 LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.lshr.next = lshr i64 %iv.lshr, 2
-; CHECK-NEXT: --> (%iv.lshr /u 4) U: [0,256) S: [0,256) Exits: 0 LoopDispositions: { %loop: Variant }
+; CHECK-NEXT: --> (%iv.lshr /u 4) U: [0,240) S: [0,240) Exits: 0 LoopDispositions: { %loop: Variant }
; CHECK-NEXT: Determining loop execution counts for: @test_lshr_arbitrary_start
; CHECK-NEXT: Loop %loop: backedge-taken count is 4
; CHECK-NEXT: Loop %loop: max backedge-taken count is 4
@@ -821,11 +821,11 @@ define void @test_lshr_start_power_of_2_plus_one() {
; CHECK-NEXT: %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {0,+,1}<%loop> U: [0,5) S: [0,5) Exits: 4 LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.lshr = phi i64 [ 1025, %entry ], [ %iv.lshr.next, %loop ]
-; CHECK-NEXT: --> %iv.lshr U: [0,1026) S: [0,1026) Exits: 4 LoopDispositions: { %loop: Variant }
+; CHECK-NEXT: --> %iv.lshr U: [4,1026) S: [4,1026) Exits: 4 LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %iv.next = add i64 %iv, 1
; CHECK-NEXT: --> {1,+,1}<%loop> U: [1,6) S: [1,6) Exits: 5 LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.lshr.next = lshr i64 %iv.lshr, 2
-; CHECK-NEXT: --> (%iv.lshr /u 4) U: [0,512) S: [0,512) Exits: 1 LoopDispositions: { %loop: Variant }
+; CHECK-NEXT: --> (%iv.lshr /u 4) U: [1,257) S: [1,257) Exits: 1 LoopDispositions: { %loop: Variant }
; CHECK-NEXT: Determining loop execution counts for: @test_lshr_start_power_of_2_plus_one
; CHECK-NEXT: Loop %loop: backedge-taken count is 4
; CHECK-NEXT: Loop %loop: max backedge-taken count is 4
More information about the llvm-commits
mailing list