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| author | Tobias Grosser <tobias@grosser.es> | 2015-06-03 09:31:30 +0300 |
|---|---|---|
| committer | Tobias Grosser <tobias@grosser.es> | 2015-06-03 09:31:30 +0300 |
| commit | cb73f150d4dee783784b5c3bb9deac4d3357624a (patch) | |
| tree | 8d4b46ce7e30c33debf031afeb6cd4ee4a01330a /polly/lib | |
| parent | dc9293d051e290ed3f3438a082cbf0d10c773245 (diff) | |
Translate power-of-two floor-division into ashr
Power-of-two floor divisions can be translated into an arithmetic shift
operation. This allows us to replace a complex lowering that requires division
operations:
%pexp.fdiv_q.0 = sub i64 %21, 128
%pexp.fdiv_q.1 = add i64 %pexp.fdiv_q.0, 1
%pexp.fdiv_q.2 = icmp slt i64 %21, 0
%pexp.fdiv_q.3 = select i1 %pexp.fdiv_q.2, i64 %pexp.fdiv_q.1, i64 %21
%pexp.fdiv_q.4 = sdiv i64 %pexp.fdiv_q.3, 128
with a simple ashr:
%polly.fdiv_q.shr = ashr i64 %21, 7
llvm-svn: 238905
Diffstat (limited to 'polly/lib')
| -rw-r--r-- | polly/lib/CodeGen/IslExprBuilder.cpp | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/polly/lib/CodeGen/IslExprBuilder.cpp b/polly/lib/CodeGen/IslExprBuilder.cpp index 60a46531f2e9..27c72486c7e0 100644 --- a/polly/lib/CodeGen/IslExprBuilder.cpp +++ b/polly/lib/CodeGen/IslExprBuilder.cpp @@ -301,6 +301,11 @@ Value *IslExprBuilder::createOpBin(__isl_take isl_ast_expr *Expr) { Res = Builder.CreateUDiv(LHS, RHS, "pexp.p_div_q"); break; case isl_ast_op_fdiv_q: { // Round towards -infty + auto &Int = dyn_cast<ConstantInt>(RHS)->getValue(); + if (Int.isPowerOf2()) { + Res = Builder.CreateAShr(LHS, Int.ceilLogBase2(), "polly.fdiv_q.shr"); + break; + } // TODO: Review code and check that this calculation does not yield // incorrect overflow in some bordercases. // |