[llvm] [llvm][SPIRV] Expose fast `popcnt` support for SPIR-V targets (PR #109845)

[Alex Voicu via llvm-commits]

================
@@ -0,0 +1,114 @@
+; RUN: opt -O3 -mtriple=spirv32-- %s -o - | llc -O3 -mtriple=spirv32-- -o - | FileCheck %s
+; RUN: %if spirv-tools %{ opt -O3 -mtriple=spirv32-- %s -o - | llc -O3 -mtriple=spirv32-- -o - -filetype=obj | spirv-val %}
+
+; RUN: opt -O3 -mtriple=spirv64-- %s -o - | llc -O3 -mtriple=spirv64-- -o - | FileCheck %s
+; RUN: %if spirv-tools %{ opt -O3 -mtriple=spirv64-- %s -o - | llc -O3 -mtriple=spirv64-- -o - -filetype=obj | spirv-val %}
+
+; Mostly copied from x86 version.
+
+;To recognize this pattern:
+;int popcount(unsigned long long a) {
+;    int c = 0;
+;    while (a) {
+;        c++;
+;        a &= a - 1;
+;    }
+;    return c;
+;}
+
+; CHECK-DAG: OpName %[[POPCNT64:.*]] "popcount_i64"
+; CHECK-DAG: OpName %[[POPCNT32:.*]] "popcount_i32"
+; CHECK-DAG: OpName %[[POPCNT2:.*]] "popcount2"
+; CHECK-DAG: %[[INT64:.*]] = OpTypeInt 64 0
+; CHECK-DAG: %[[INT32:.*]] = OpTypeInt 32 0
+
+define i32 @popcount_i64(i64 %a) nounwind uwtable readnone ssp {
+entry:
+  %tobool3 = icmp eq i64 %a, 0
+  br i1 %tobool3, label %while.end, label %while.body
+
+while.body:                                       ; preds = %entry, %while.body
+  %c.05 = phi i32 [ %inc, %while.body ], [ 0, %entry ]
+  %a.addr.04 = phi i64 [ %and, %while.body ], [ %a, %entry ]
+  %inc = add nsw i32 %c.05, 1
+  %sub = add i64 %a.addr.04, -1
+  %and = and i64 %sub, %a.addr.04
+  %tobool = icmp eq i64 %and, 0
+  br i1 %tobool, label %while.end, label %while.body
+
+while.end:                                        ; preds = %while.body, %entry
+  %c.0.lcssa = phi i32 [ 0, %entry ], [ %inc, %while.body ]
+  ret i32 %c.0.lcssa
+}
+; CHECK-DAG: %[[POPCNT64]] = OpFunction
+; CHECK: %[[A:.*]] = OpFunctionParameter %[[INT64]]
+; CHECK-DAG: %{{.+}} = OpBitCount %[[INT64]] %[[A]]
+; CHECK-DAG: OpFunctionEnd
+
+
+define i32 @popcount_i32(i32 %a) nounwind uwtable readnone ssp {
+entry:
+  %tobool3 = icmp eq i32 %a, 0
+  br i1 %tobool3, label %while.end, label %while.body
+
+while.body:                                       ; preds = %entry, %while.body
+  %c.05 = phi i32 [ %inc, %while.body ], [ 0, %entry ]
+  %a.addr.04 = phi i32 [ %and, %while.body ], [ %a, %entry ]
+  %inc = add nsw i32 %c.05, 1
+  %sub = add i32 %a.addr.04, -1
+  %and = and i32 %sub, %a.addr.04
+  %tobool = icmp eq i32 %and, 0
+  br i1 %tobool, label %while.end, label %while.body
+
+while.end:                                        ; preds = %while.body, %entry
+  %c.0.lcssa = phi i32 [ 0, %entry ], [ %inc, %while.body ]
+  ret i32 %c.0.lcssa
+}
+; CHECK: %[[POPCNT32]] = OpFunction
+; CHECK: %[[A:.*]] = OpFunctionParameter %[[INT32]]
+; CHECK-DAG: %{{.*}} = OpBitCount %[[INT32]] %[[A]]
+; CHECK-DAG: OpFunctionEnd
+
+; To recognize this pattern:
+;int popcount(unsigned long long a, int mydata1, int mydata2) {
+;    int c = 0;
+;    while (a) {
+;        c++;
+;        a &= a - 1;
+;        mydata1 *= c;
+;        mydata2 *= (int)a;
+;    }
+;    return c + mydata1 + mydata2;
+;}
+
+define i32 @popcount2(i64 %a, i32 %mydata1, i32 %mydata2) nounwind uwtable readnone ssp {
+entry:
+  %tobool9 = icmp eq i64 %a, 0
+  br i1 %tobool9, label %while.end, label %while.body
+
+while.body:                                       ; preds = %entry, %while.body
+  %c.013 = phi i32 [ %inc, %while.body ], [ 0, %entry ]
+  %mydata2.addr.012 = phi i32 [ %mul1, %while.body ], [ %mydata2, %entry ]
+  %mydata1.addr.011 = phi i32 [ %mul, %while.body ], [ %mydata1, %entry ]
+  %a.addr.010 = phi i64 [ %and, %while.body ], [ %a, %entry ]
+  %inc = add nsw i32 %c.013, 1
+  %sub = add i64 %a.addr.010, -1
+  %and = and i64 %sub, %a.addr.010
+  %mul = mul nsw i32 %inc, %mydata1.addr.011
+  %conv = trunc i64 %and to i32
+  %mul1 = mul nsw i32 %conv, %mydata2.addr.012
+  %tobool = icmp eq i64 %and, 0
+  br i1 %tobool, label %while.end, label %while.body
+
+while.end:                                        ; preds = %while.body, %entry
+  %c.0.lcssa = phi i32 [ 0, %entry ], [ %inc, %while.body ]
+  %mydata2.addr.0.lcssa = phi i32 [ %mydata2, %entry ], [ %mul1, %while.body ]
+  %mydata1.addr.0.lcssa = phi i32 [ %mydata1, %entry ], [ %mul, %while.body ]
+  %add = add i32 %mydata2.addr.0.lcssa, %mydata1.addr.0.lcssa
+  %add2 = add i32 %add, %c.0.lcssa
+  ret i32 %add2
+}
+; CHECK: %[[POPCNT2]] = OpFunction
+; CHECK: %[[A:.*]] = OpFunctionParameter %[[INT64]]
+; CHECK-DAG: %{{.*}} = OpBitCount %[[INT64]] %[[A]]
+; CHECK-DAG: OpFunctionEnd
----------------
AlexVlx wrote:

Done.

https://github.com/llvm/llvm-project/pull/109845