Exploit non-negative numerators

isl marks known non-negative numerators in modulo (and soon also division)
operations. We now exploit this by generating unsigned operations. This is
beneficial as unsigned operations with power-of-two denominators will be
translated by isl to fast bitshift or bitwise and operations.

llvm-svn: 238577

3 files changed, 128 insertions, 7 deletions

diff --git a/polly/lib/CodeGen/IslExprBuilder.cpp b/polly/lib/CodeGen/IslExprBuilder.cpp
index b502e7a0718..60a46531f2e 100644
--- a/polly/lib/CodeGen/IslExprBuilder.cpp
+++ b/polly/lib/CodeGen/IslExprBuilder.cpp
@@ -295,8 +295,10 @@ Value *IslExprBuilder::createOpBin(__isl_take isl_ast_expr *Expr) {
     Res = Builder.CreateNSWMul(LHS, RHS);
     break;
   case isl_ast_op_div:
+    Res = Builder.CreateSDiv(LHS, RHS, "pexp.div");
+    break;
   case isl_ast_op_pdiv_q: // Dividend is non-negative
-    Res = Builder.CreateSDiv(LHS, RHS);
+    Res = Builder.CreateUDiv(LHS, RHS, "pexp.p_div_q");
     break;
   case isl_ast_op_fdiv_q: { // Round towards -infty
     // TODO: Review code and check that this calculation does not yield
@@ -305,16 +307,20 @@ Value *IslExprBuilder::createOpBin(__isl_take isl_ast_expr *Expr) {
     // floord(n,d) ((n < 0) ? (n - d + 1) : n) / d
     Value *One = ConstantInt::get(MaxType, 1);
     Value *Zero = ConstantInt::get(MaxType, 0);
-    Value *Sum1 = Builder.CreateSub(LHS, RHS);
-    Value *Sum2 = Builder.CreateAdd(Sum1, One);
-    Value *isNegative = Builder.CreateICmpSLT(LHS, Zero);
-    Value *Dividend = Builder.CreateSelect(isNegative, Sum2, LHS);
-    Res = Builder.CreateSDiv(Dividend, RHS);
+    Value *Sum1 = Builder.CreateSub(LHS, RHS, "pexp.fdiv_q.0");
+    Value *Sum2 = Builder.CreateAdd(Sum1, One, "pexp.fdiv_q.1");
+    Value *isNegative = Builder.CreateICmpSLT(LHS, Zero, "pexp.fdiv_q.2");
+    Value *Dividend =
+        Builder.CreateSelect(isNegative, Sum2, LHS, "pexp.fdiv_q.3");
+    Res = Builder.CreateSDiv(Dividend, RHS, "pexp.fdiv_q.4");
     break;
   }
   case isl_ast_op_pdiv_r: // Dividend is non-negative
+    Res = Builder.CreateURem(LHS, RHS, "pexp.pdiv_r");
+    break;
+
   case isl_ast_op_zdiv_r: // Result only compared against zero
-    Res = Builder.CreateSRem(LHS, RHS);
+    Res = Builder.CreateURem(LHS, RHS, "pexp.zdiv_r");
     break;
   }
 
diff --git a/polly/test/Isl/CodeGen/exprModDiv.ll b/polly/test/Isl/CodeGen/exprModDiv.ll
new file mode 100644
index 00000000000..e471e6b1f80
--- /dev/null
+++ b/polly/test/Isl/CodeGen/exprModDiv.ll
@@ -0,0 +1,78 @@
+; RUN: opt %loadPolly -polly-import-jscop -polly-import-jscop-dir=%S -polly-codegen -S < %s | FileCheck %s
+;
+;    void exprModDiv(float *A, float *B, float *C, long N, long p) {
+;      for (long i = 0; i < N; i++)
+;        C[i] += A[i] + B[i] + A[p] + B[p];
+;    }
+;
+;
+; This test case changes the access functions such that the resulting index
+; expressions are modulo or division operations. We test that the code we
+; generate takes advantage of knowledge about unsigned numerators. This is
+; useful as LLVM will translate urem and udiv operations with power-of-two
+; denominators to fast bitwise and or shift operations.
+
+; A[i % 128]
+; CHECK:  %pexp.pdiv_r = urem i64 %polly.indvar, 128
+; CHECK:  %polly.access.A6 = getelementptr float, float* %A, i64 %pexp.pdiv_r
+
+; A[i / 128]
+; CHECK:  %pexp.div = sdiv i64 %polly.indvar, 128
+; CHECK:  %polly.access.B8 = getelementptr float, float* %B, i64 %pexp.div
+;
+; FIXME: Make isl mark this as an udiv expression.
+
+; #define floord(n,d) ((n < 0) ? (n - d + 1) : n) / d
+; A[p + 128 * floord(-p - 1, 128) + 128]
+; CHECK:  %20 = sub nsw i64 0, %p
+; CHECK:  %21 = sub nsw i64 %20, 1
+; CHECK:  %pexp.fdiv_q.0 = sub i64 %21, 128
+; CHECK:  %pexp.fdiv_q.1 = add i64 %pexp.fdiv_q.0, 1
+; CHECK:  %pexp.fdiv_q.2 = icmp slt i64 %21, 0
+; CHECK:  %pexp.fdiv_q.3 = select i1 %pexp.fdiv_q.2, i64 %pexp.fdiv_q.1, i64 %21
+; CHECK:  %pexp.fdiv_q.4 = sdiv i64 %pexp.fdiv_q.3, 128
+; CHECK:  %22 = mul nsw i64 128, %pexp.fdiv_q.4
+; CHECK:  %23 = add nsw i64 %p, %22
+; CHECK:  %24 = add nsw i64 %23, 128
+; CHECK:  %polly.access.A10 = getelementptr float, float* %A, i64 %24
+
+; A[p / 128]
+; CHECK:  %pexp.div12 = sdiv i64 %p, 128
+; CHECK:  %polly.access.B13 = getelementptr float, float* %B, i64 %pexp.div12
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @exprModDiv(float* %A, float* %B, float* %C, i64 %N, i64 %p) {
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.inc, %entry
+  %i.0 = phi i64 [ 0, %entry ], [ %inc, %for.inc ]
+  %cmp = icmp slt i64 %i.0, %N
+  br i1 %cmp, label %for.body, label %for.end
+
+for.body:                                         ; preds = %for.cond
+  %arrayidx = getelementptr inbounds float, float* %A, i64 %i.0
+  %tmp = load float, float* %arrayidx, align 4
+  %arrayidx1 = getelementptr inbounds float, float* %B, i64 %i.0
+  %tmp1 = load float, float* %arrayidx1, align 4
+  %add = fadd float %tmp, %tmp1
+  %arrayidx2 = getelementptr inbounds float, float* %A, i64 %p
+  %tmp2 = load float, float* %arrayidx2, align 4
+  %add3 = fadd float %add, %tmp2
+  %arrayidx4 = getelementptr inbounds float, float* %B, i64 %p
+  %tmp3 = load float, float* %arrayidx4, align 4
+  %add5 = fadd float %add3, %tmp3
+  %arrayidx6 = getelementptr inbounds float, float* %C, i64 %i.0
+  %tmp4 = load float, float* %arrayidx6, align 4
+  %add7 = fadd float %tmp4, %add5
+  store float %add7, float* %arrayidx6, align 4
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body
+  %inc = add nuw nsw i64 %i.0, 1
+  br label %for.cond
+
+for.end:                                          ; preds = %for.cond
+  ret void
+}
diff --git a/polly/test/Isl/CodeGen/exprModDiv___%for.cond---%for.end.jscop b/polly/test/Isl/CodeGen/exprModDiv___%for.cond---%for.end.jscop
new file mode 100644
index 00000000000..5309f8ab577
--- /dev/null
+++ b/polly/test/Isl/CodeGen/exprModDiv___%for.cond---%for.end.jscop
@@ -0,0 +1,37 @@
+{
+   "context" : "[N, p] -> {  : N >= -9223372036854775808 and N <= 9223372036854775807 and p >= -9223372036854775808 and p <= 9223372036854775807 }",
+   "name" : "for.cond => for.end",
+   "statements" : [
+      {
+         "accesses" : [
+            {
+               "kind" : "read",
+               "relation" : "[N, p] -> { Stmt_for_body[i0] -> MemRef_A[i0 % 128] }"
+            },
+            {
+               "kind" : "read",
+               "relation" : "[N, p] -> { Stmt_for_body[i0] -> MemRef_B[i0 / 128] }"
+            },
+            {
+               "kind" : "read",
+               "relation" : "[N, p] -> { Stmt_for_body[i0] -> MemRef_A[p % 128] }"
+            },
+            {
+               "kind" : "read",
+               "relation" : "[N, p] -> { Stmt_for_body[i0] -> MemRef_B[p / 128] }"
+            },
+            {
+               "kind" : "read",
+               "relation" : "[N, p] -> { Stmt_for_body[i0] -> MemRef_C[i0] }"
+            },
+            {
+               "kind" : "write",
+               "relation" : "[N, p] -> { Stmt_for_body[i0] -> MemRef_C[i0] }"
+            }
+         ],
+         "domain" : "[N, p] -> { Stmt_for_body[i0] : i0 >= 0 and N >= 1 and i0 <= -1 + N }",
+         "name" : "Stmt_for_body",
+         "schedule" : "[N, p] -> { Stmt_for_body[i0] -> [i0] }"
+      }
+   ]
+}