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[ScopInfo] Add support for wrap-around of integers in unsigned comparisons. 

This is one possible solution to implement wrap-arounds for integers in
unsigned icmp operations. For example,

    store i32 -1, i32* %A_addr
    %0 = load i32, i32* %A_addr
    %1 = icmp ult i32 %0, 0

%1 should hold false, because under the assumption of unsigned integers,
-1 should wrap around to 2^32-1. However, previously. it was assumed
that the MSB (Most Significant Bit - aka the Sign bit) was never set for
integers in unsigned operations.

This patch modifies the buildConditionSets function in ScopInfo.cpp to
give better information about the integers in these unsigned
comparisons.

Contributed-by: Annanay Agarwal <cs14btech11001@iith.ac.in>

Differential Revision: https://reviews.llvm.org/D35464

llvm-svn: 308608
This commit is contained in:
Michael Kruse 2017-07-20 12:37:02 +00:00
parent e9599e39fe
commit 0865585eab
9 changed files with 261 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

78
polly/lib/Analysis/ScopInfo.cpp
View File

@ -1536,6 +1536,47 @@ buildConditionSets(Scop &S, BasicBlock *BB, SwitchInst *SI, Loop *L,
return true;
}
/// Build condition sets for unsigned ICmpInst(s).
/// Special handling is required for unsigned operands to ensure that if
/// MSB (aka the Sign bit) is set for an operands in an unsigned ICmpInst
/// it should wrap around.
///
/// @param IsStrictUpperBound holds information on the predicate relation
/// between TestVal and UpperBound, i.e,
/// TestVal < UpperBound OR TestVal <= UpperBound
static __isl_give isl_set *
buildUnsignedConditionSets(Scop &S, BasicBlock *BB, Value *Condition,
__isl_keep isl_set *Domain, const SCEV *SCEV_TestVal,
const SCEV *SCEV_UpperBound,
DenseMap<BasicBlock *, isl::set> &InvalidDomainMap,
bool IsStrictUpperBound) {
// Do not take NonNeg assumption on TestVal
// as it might have MSB (Sign bit) set.
isl_pw_aff *TestVal = getPwAff(S, BB, InvalidDomainMap, SCEV_TestVal, false);
// Take NonNeg assumption on UpperBound.
isl_pw_aff *UpperBound =
getPwAff(S, BB, InvalidDomainMap, SCEV_UpperBound, true);
// 0 <= TestVal
isl_set *First =
isl_pw_aff_le_set(isl_pw_aff_zero_on_domain(isl_local_space_from_space(
isl_pw_aff_get_domain_space(TestVal))),
isl_pw_aff_copy(TestVal));
isl_set *Second;
if (IsStrictUpperBound)
// TestVal < UpperBound
Second = isl_pw_aff_lt_set(TestVal, UpperBound);
else
// TestVal <= UpperBound
Second = isl_pw_aff_le_set(TestVal, UpperBound);
isl_set *ConsequenceCondSet = isl_set_intersect(First, Second);
ConsequenceCondSet = setDimensionIds(Domain, ConsequenceCondSet);
return ConsequenceCondSet;
}
/// Build the conditions sets for the branch condition @p Condition in
/// the @p Domain.
///
@ -1590,12 +1631,37 @@ buildConditionSets(Scop &S, BasicBlock *BB, Value *Condition,
// to be set. The comparison is equal to a signed comparison under this
// assumption.
bool NonNeg = ICond->isUnsigned();
LHS = getPwAff(S, BB, InvalidDomainMap,
SE.getSCEVAtScope(ICond->getOperand(0), L), NonNeg);
RHS = getPwAff(S, BB, InvalidDomainMap,
SE.getSCEVAtScope(ICond->getOperand(1), L), NonNeg);
ConsequenceCondSet =
buildConditionSet(ICond->getPredicate(), LHS, RHS, Domain);
const SCEV *LeftOperand = SE.getSCEVAtScope(ICond->getOperand(0), L),
*RightOperand = SE.getSCEVAtScope(ICond->getOperand(1), L);
switch (ICond->getPredicate()) {
case ICmpInst::ICMP_ULT:
ConsequenceCondSet =
buildUnsignedConditionSets(S, BB, Condition, Domain, LeftOperand,
RightOperand, InvalidDomainMap, true);
break;
case ICmpInst::ICMP_ULE:
ConsequenceCondSet =
buildUnsignedConditionSets(S, BB, Condition, Domain, LeftOperand,
RightOperand, InvalidDomainMap, false);
break;
case ICmpInst::ICMP_UGT:
ConsequenceCondSet =
buildUnsignedConditionSets(S, BB, Condition, Domain, RightOperand,
LeftOperand, InvalidDomainMap, true);
break;
case ICmpInst::ICMP_UGE:
ConsequenceCondSet =
buildUnsignedConditionSets(S, BB, Condition, Domain, RightOperand,
LeftOperand, InvalidDomainMap, false);
break;
default:
LHS = getPwAff(S, BB, InvalidDomainMap, LeftOperand, NonNeg);
RHS = getPwAff(S, BB, InvalidDomainMap, RightOperand, NonNeg);
ConsequenceCondSet =
buildConditionSet(ICond->getPredicate(), LHS, RHS, Domain);
break;
}
}
// If no terminator was given we are only looking for parameter constraints

4
polly/test/ScopInfo/simple_loop_unsigned.ll
View File

@ -10,10 +10,10 @@
; CHECK: Assumed Context:
; CHECK-NEXT: [N] -> { : }
; CHECK-NEXT: Invalid Context:
; CHECK-NEXT: [N] -> { : N < 0 }
; CHECK-NEXT: [N] -> { : 1 = 0 }
;
; CHECK: Domain :=
; CHECK-NEXT: [N] -> { Stmt_bb[i0] : 0 <= i0 < N; Stmt_bb[0] : N <= 0 };
; CHECK-NEXT: [N] -> { Stmt_bb[i0] : 0 <= i0 < N; Stmt_bb[0] : N = 0 };
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"

2
polly/test/ScopInfo/simple_loop_unsigned_3.ll
View File

@ -4,7 +4,7 @@
; CHECK-NEXT: [N] -> { : }
;
; CHECK: Domain :=
; CHECK-NEXT: [N] -> { Stmt_bb[i0] : 0 < i0 <= 1000 - N; Stmt_bb[0] };
; CHECK-NEXT: [N] -> { Stmt_bb[0] };
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"

46
polly/test/ScopInfo/unsigned_wrap_uge.ll Normal file
View File

@ -0,0 +1,46 @@
; RUN: opt %loadPolly -polly-scops -analyze < %s | FileCheck %s
;
; Unsigned wrap-around check.
;
; for (int i = -1; i < 65 ; i ++ )
; if ( 63 >= (unsigned)i )
; A[i] = 42;
define void @func(double* noalias nonnull %A) {
entry:
br label %for
for:
%j = phi i32 [-1, %entry], [%j.inc, %inc]
%j.cmp = icmp slt i32 %j, 65
br i1 %j.cmp, label %body, label %exit
body:
%inbounds = icmp uge i32 63, %j
br i1 %inbounds, label %ifinbounds, label %ifoutbounds
ifinbounds:
%A_idx = getelementptr inbounds double, double* %A, i32 %j
store double 42.0, double* %A_idx
br label %inc
ifoutbounds:
br label %inc
inc:
%j.inc = add nuw nsw i32 %j, 1
br label %for
exit:
br label %return
return:
ret void
}
; CHECK: Region: %for---%return
; CHECK: Domain :=
; CHECK-NEXT: { Stmt_ifinbounds[i0] : 0 < i0 <= 64 };

46
polly/test/ScopInfo/unsigned_wrap_ugt.ll Normal file
View File

@ -0,0 +1,46 @@
; RUN: opt %loadPolly -polly-scops -analyze < %s | FileCheck %s
;
; Unsigned wrap-around check.
;
; for (int i = -1; i < 65 ; i ++ )
; if ( 64 > (unsigned)i )
; A[i] = 42;
define void @func(double* noalias nonnull %A) {
entry:
br label %for
for:
%j = phi i32 [-1, %entry], [%j.inc, %inc]
%j.cmp = icmp slt i32 %j, 65
br i1 %j.cmp, label %body, label %exit
body:
%inbounds = icmp ugt i32 64, %j
br i1 %inbounds, label %ifinbounds, label %ifoutbounds
ifinbounds:
%A_idx = getelementptr inbounds double, double* %A, i32 %j
store double 42.0, double* %A_idx
br label %inc
ifoutbounds:
br label %inc
inc:
%j.inc = add nuw nsw i32 %j, 1
br label %for
exit:
br label %return
return:
ret void
}
; CHECK: Region: %for---%return
; CHECK: Domain :=
; CHECK-NEXT: { Stmt_ifinbounds[i0] : 0 < i0 <= 64 };

46
polly/test/ScopInfo/unsigned_wrap_ule.ll Normal file
View File

@ -0,0 +1,46 @@
; RUN: opt %loadPolly -polly-scops -analyze < %s | FileCheck %s
;
; Unsigned wrap-around check.
;
; for (int i = -1; i < 65 ; i ++ )
; if ( (unsigned)i <= 63 )
; A[i] = 42;
define void @func(double* noalias nonnull %A) {
entry:
br label %for
for:
%j = phi i32 [-1, %entry], [%j.inc, %inc]
%j.cmp = icmp slt i32 %j, 65
br i1 %j.cmp, label %body, label %exit
body:
%inbounds = icmp ule i32 %j, 63
br i1 %inbounds, label %ifinbounds, label %ifoutbounds
ifinbounds:
%A_idx = getelementptr inbounds double, double* %A, i32 %j
store double 42.0, double* %A_idx
br label %inc
ifoutbounds:
br label %inc
inc:
%j.inc = add nuw nsw i32 %j, 1
br label %for
exit:
br label %return
return:
ret void
}
; CHECK: Region: %for---%return
; CHECK: Domain :=
; CHECK-NEXT: { Stmt_ifinbounds[i0] : 0 < i0 <= 64 };

46
polly/test/ScopInfo/unsigned_wrap_ult.ll Normal file
View File

@ -0,0 +1,46 @@
; RUN: opt %loadPolly -polly-scops -analyze < %s | FileCheck %s
;
; Unsigned wrap-around check.
;
; for (int i = -1; i < 65 ; i ++ )
; if ( (unsigned)i < 64 )
; A[i] = 42;
define void @func(double* noalias nonnull %A) {
entry:
br label %for
for:
%j = phi i32 [-1, %entry], [%j.inc, %inc]
%j.cmp = icmp slt i32 %j, 65
br i1 %j.cmp, label %body, label %exit
body:
%inbounds = icmp ult i32 %j, 64
br i1 %inbounds, label %ifinbounds, label %ifoutbounds
ifinbounds:
%A_idx = getelementptr inbounds double, double* %A, i32 %j
store double 42.0, double* %A_idx
br label %inc
ifoutbounds:
br label %inc
inc:
%j.inc = add nuw nsw i32 %j, 1
br label %for
exit:
br label %return
return:
ret void
}
; CHECK: Region: %for---%return
; CHECK: Domain :=
; CHECK-NEXT: { Stmt_ifinbounds[i0] : 0 < i0 <= 64 };

2
polly/test/ScopInfo/zero_ext_of_truncate.ll
View File

@ -16,7 +16,7 @@
; CHECK-NEXT: [N, tmp, M] -> { : N < 0 or (N > 0 and tmp >= 128) or (N > 0 and tmp < 0) or (N > 0 and M < 0) }
;
; CHECK: Domain :=
; CHECK-NEXT: [N, tmp, M] -> { Stmt_if_then[i0] : M > tmp and 0 <= i0 < N };
; CHECK-NEXT: [N, tmp, M] -> { Stmt_if_then[i0] : tmp >= 0 and M > tmp and 0 <= i0 < N };
;
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"

2
polly/test/ScopInfo/zero_ext_of_truncate_2.ll
View File

@ -15,7 +15,7 @@
; CHECK-NEXT: [N, tmp] -> { : N > 0 and (tmp < 0 or tmp >= 2147483648) }
;
; CHECK: Domain :=
; CHECK-NEXT: [N, tmp] -> { Stmt_if_then[i0] : i0 > tmp and 0 <= i0 < N };
; CHECK-NEXT: [N, tmp] -> { Stmt_if_then[i0] : tmp >= 0 and tmp < i0 < N };
;
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"