make -d:nimFpRoundtrips work consistently in vm vs rt, fix #18400, etc (#18531)

* compiler/vmhooks: add getVar to allow vmops with var params
* addFloat vmops with var param
* cgen now renders float32 literals in c backend using roundtrip float to string

9 files changed, 44 insertions, 37 deletions

diff --git a/compiler/ast.nim b/compiler/ast.nim
index f1f73dcee..8b836e088 100644
--- a/compiler/ast.nim
+++ b/compiler/ast.nim
@@ -652,7 +652,7 @@ type
     mUnaryMinusI, mUnaryMinusI64, mAbsI, mNot,
     mUnaryPlusI, mBitnotI,
     mUnaryPlusF64, mUnaryMinusF64,
-    mCharToStr, mBoolToStr, mIntToStr, mInt64ToStr, mFloatToStr, mCStrToStr,
+    mCharToStr, mBoolToStr, mIntToStr, mInt64ToStr, mCStrToStr,
     mStrToStr, mEnumToStr,
     mAnd, mOr,
     mImplies, mIff, mExists, mForall, mOld,
@@ -720,7 +720,7 @@ const
     mEqRef, mEqProc, mLePtr, mLtPtr, mEqCString, mXor,
     mUnaryMinusI, mUnaryMinusI64, mAbsI, mNot, mUnaryPlusI, mBitnotI,
     mUnaryPlusF64, mUnaryMinusF64,
-    mCharToStr, mBoolToStr, mIntToStr, mInt64ToStr, mFloatToStr, mCStrToStr,
+    mCharToStr, mBoolToStr, mIntToStr, mInt64ToStr, mCStrToStr,
     mStrToStr, mEnumToStr,
     mAnd, mOr,
     mEqStr, mLeStr, mLtStr,
diff --git a/compiler/ccgexprs.nim b/compiler/ccgexprs.nim
index 09326ceeb..79c73b602 100644
--- a/compiler/ccgexprs.nim
+++ b/compiler/ccgexprs.nim
@@ -94,9 +94,12 @@ proc genLiteral(p: BProc, n: PNode, ty: PType): Rope =
     else:
       result = makeCString(n.strVal)
   of nkFloatLit, nkFloat64Lit:
-    result = rope(n.floatVal.toStrMaxPrecision)
+    if ty.kind == tyFloat32:
+      result = rope(n.floatVal.float32.toStrMaxPrecision)
+    else:
+      result = rope(n.floatVal.toStrMaxPrecision)
   of nkFloat32Lit:
-    result = rope(n.floatVal.toStrMaxPrecision("f"))
+    result = rope(n.floatVal.float32.toStrMaxPrecision)
   else:
     internalError(p.config, n.info, "genLiteral(" & $n.kind & ')')
     result = nil
@@ -2300,11 +2303,6 @@ proc genMagicExpr(p: BProc, e: PNode, d: var TLoc, op: TMagic) =
   of mInt64ToStr: genDollar(p, e, d, "#nimInt64ToStr($1)")
   of mBoolToStr: genDollar(p, e, d, "#nimBoolToStr($1)")
   of mCharToStr: genDollar(p, e, d, "#nimCharToStr($1)")
-  of mFloatToStr:
-    if e[1].typ.skipTypes(abstractInst).kind == tyFloat32:
-      genDollar(p, e, d, "#nimFloat32ToStr($1)")
-    else:
-      genDollar(p, e, d, "#nimFloatToStr($1)")
   of mCStrToStr: genDollar(p, e, d, "#cstrToNimstr($1)")
   of mStrToStr, mUnown: expr(p, e[1], d)
   of mIsolate: genCall(p, e, d)
diff --git a/compiler/jsgen.nim b/compiler/jsgen.nim
index 82fba02a6..4b89b0cde 100644
--- a/compiler/jsgen.nim
+++ b/compiler/jsgen.nim
@@ -434,7 +434,6 @@ const # magic checked op; magic unchecked op;
     mBoolToStr: ["nimBoolToStr", "nimBoolToStr"],
     mIntToStr: ["cstrToNimstr", "cstrToNimstr"],
     mInt64ToStr: ["cstrToNimstr", "cstrToNimstr"],
-    mFloatToStr: ["cstrToNimstr", "cstrToNimstr"],
     mCStrToStr: ["cstrToNimstr", "cstrToNimstr"],
     mStrToStr: ["", ""]]
 
@@ -656,9 +655,6 @@ proc arithAux(p: PProc, n: PNode, r: var TCompRes, op: TMagic) =
   of mBoolToStr: applyFormat("nimBoolToStr($1)", "nimBoolToStr($1)")
   of mIntToStr: applyFormat("cstrToNimstr(($1) + \"\")", "cstrToNimstr(($1) + \"\")")
   of mInt64ToStr: applyFormat("cstrToNimstr(($1) + \"\")", "cstrToNimstr(($1) + \"\")")
-  of mFloatToStr:
-    useMagic(p, "nimFloatToString")
-    applyFormat "cstrToNimstr(nimFloatToString($1))"
   of mCStrToStr: applyFormat("cstrToNimstr($1)", "cstrToNimstr($1)")
   of mStrToStr, mUnown, mIsolate: applyFormat("$1", "$1")
   else:
@@ -682,8 +678,7 @@ proc arith(p: PProc, n: PNode, r: var TCompRes, op: TMagic) =
     gen(p, n[1], x)
     gen(p, n[2], y)
     r.res = "($1 >>> $2)" % [x.rdLoc, y.rdLoc]
-  of mCharToStr, mBoolToStr, mIntToStr, mInt64ToStr, mFloatToStr,
-      mCStrToStr, mStrToStr, mEnumToStr:
+  of mCharToStr, mBoolToStr, mIntToStr, mInt64ToStr, mCStrToStr, mStrToStr, mEnumToStr:
     arithAux(p, n, r, op)
   of mEqRef:
     if mapType(n[1].typ) != etyBaseIndex:
diff --git a/compiler/nim.cfg b/compiler/nim.cfg
index 9ecd00b0b..f10d847ac 100644
--- a/compiler/nim.cfg
+++ b/compiler/nim.cfg
@@ -4,6 +4,7 @@ hint:XDeclaredButNotUsed:off
 
 define:booting
 define:nimcore
+define:nimFpRoundtrips
 
 #import:"$projectpath/testability"
 
diff --git a/compiler/rodutils.nim b/compiler/rodutils.nim
index e13b08e05..a4f7a5146 100644
--- a/compiler/rodutils.nim
+++ b/compiler/rodutils.nim
@@ -39,7 +39,10 @@ when not declared(signbit):
   proc signbit*(x: SomeFloat): bool {.inline.} =
     result = c_signbit(x) != 0
 
-proc toStrMaxPrecision*(f: BiggestFloat, literalPostfix = ""): string =
+import system/formatfloat
+
+proc toStrMaxPrecision*(f: BiggestFloat | float32): string =
+  const literalPostfix = when f is float32: "f" else: ""
   case classify(f)
   of fcNan:
     if signbit(f):
@@ -55,9 +58,8 @@ proc toStrMaxPrecision*(f: BiggestFloat, literalPostfix = ""): string =
   of fcNegInf:
     result = "-INF"
   else:
-    result = newString(81)
-    let n = c_snprintf(result.cstring, result.len.uint, "%#.16e%s", f, literalPostfix.cstring)
-    setLen(result, n)
+    result.addFloatRoundtrip(f)
+    result.add literalPostfix
 
 proc encodeStr*(s: string, result: var string) =
   for i in 0..<s.len:
diff --git a/compiler/semfold.nim b/compiler/semfold.nim
index 04ed73209..e5f0643bc 100644
--- a/compiler/semfold.nim
+++ b/compiler/semfold.nim
@@ -290,7 +290,6 @@ proc evalOp(m: TMagic, n, a, b, c: PNode; idgen: IdGenerator; g: ModuleGraph): P
   of mBoolToStr:
     if getOrdValue(a) == 0: result = newStrNodeT("false", n, g)
     else: result = newStrNodeT("true", n, g)
-  of mFloatToStr: result = newStrNodeT($getFloat(a), n, g)
   of mCStrToStr, mCharToStr:
     if a.kind == nkBracket:
       var s = ""
diff --git a/compiler/vmgen.nim b/compiler/vmgen.nim
index e5e4a854e..be86550ae 100644
--- a/compiler/vmgen.nim
+++ b/compiler/vmgen.nim
@@ -1127,8 +1127,7 @@ proc genMagic(c: PCtx; n: PNode; dest: var TDest; m: TMagic) =
     let t = skipTypes(n.typ, abstractVar-{tyTypeDesc})
     if t.kind in {tyUInt8..tyUInt32} or (t.kind == tyUInt and t.size < 8):
       c.gABC(n, opcNarrowU, dest, TRegister(t.size*8))
-  of mCharToStr, mBoolToStr, mIntToStr, mInt64ToStr,
-     mFloatToStr, mCStrToStr, mStrToStr, mEnumToStr:
+  of mCharToStr, mBoolToStr, mIntToStr, mInt64ToStr, mCStrToStr, mStrToStr, mEnumToStr:
     genConv(c, n, n[1], dest)
   of mEqStr, mEqCString: genBinaryABC(c, n, dest, opcEqStr)
   of mLeStr: genBinaryABC(c, n, dest, opcLeStr)
diff --git a/compiler/vmhooks.nim b/compiler/vmhooks.nim
index 573d84853..1ede87e5e 100644
--- a/compiler/vmhooks.nim
+++ b/compiler/vmhooks.nim
@@ -36,10 +36,14 @@ proc setResult*(a: VmArgs; v: seq[string]) =
   for x in v: n.add newStrNode(nkStrLit, x)
   a.slots[a.ra].node = n
 
-template getX(k, field) {.dirty.} =
+template getReg(a, i): untyped =
   doAssert i < a.rc-1
-  doAssert a.slots[i+a.rb+1].kind == k
-  result = a.slots[i+a.rb+1].field
+  a.slots[i+a.rb+1].unsafeAddr
+
+template getX(k, field): untyped {.dirty.} =
+  let p = getReg(a, i)
+  doAssert p.kind == k, $p.kind
+  p.field
 
 proc numArgs*(a: VmArgs): int =
   result = a.rc-1
@@ -47,19 +51,17 @@ proc numArgs*(a: VmArgs): int =
 proc getInt*(a: VmArgs; i: Natural): BiggestInt = getX(rkInt, intVal)
 proc getBool*(a: VmArgs; i: Natural): bool = getInt(a, i) != 0
 proc getFloat*(a: VmArgs; i: Natural): BiggestFloat = getX(rkFloat, floatVal)
-proc getString*(a: VmArgs; i: Natural): string =
-  doAssert i < a.rc-1
-  doAssert a.slots[i+a.rb+1].kind == rkNode
-  result = a.slots[i+a.rb+1].node.strVal
-
-proc getNode*(a: VmArgs; i: Natural): PNode =
-  doAssert i < a.rc-1
-  doAssert a.slots[i+a.rb+1].kind == rkNode
-  result = a.slots[i+a.rb+1].node
+proc getNode*(a: VmArgs; i: Natural): PNode = getX(rkNode, node)
+proc getString*(a: VmArgs; i: Natural): string = getX(rkNode, node).strVal
+proc getVar*(a: VmArgs; i: Natural): PNode =
+  let p = getReg(a, i)
+  # depending on whether we come from top-level or proc scope, we need to consider 2 cases
+  case p.kind
+  of rkRegisterAddr: result = p.regAddr.node
+  of rkNodeAddr: result = p.nodeAddr[]
+  else: doAssert false, $p.kind
 
 proc getNodeAddr*(a: VmArgs; i: Natural): PNode =
-  doAssert i < a.rc-1
-  doAssert a.slots[i+a.rb+1].kind == rkNodeAddr
-  let nodeAddr = a.slots[i+a.rb+1].nodeAddr
+  let nodeAddr = getX(rkNodeAddr, nodeAddr)
   doAssert nodeAddr != nil
   result = nodeAddr[]
diff --git a/compiler/vmops.nim b/compiler/vmops.nim
index 283306ecc..bc331bbcd 100644
--- a/compiler/vmops.nim
+++ b/compiler/vmops.nim
@@ -27,6 +27,7 @@ from std/md5 import getMD5
 from std/times import cpuTime
 from std/hashes import hash
 from std/osproc import nil
+from system/formatfloat import addFloatRoundtrip, addFloatSprintf
 
 from sighashes import symBodyDigest
 
@@ -325,3 +326,13 @@ proc registerAdditionalOps*(c: PCtx) =
   registerCallback c, "stdlib.typetraits.hasClosureImpl", proc (a: VmArgs) =
     let fn = getNode(a, 0)
     setResult(a, fn.kind == nkClosure or (fn.typ != nil and fn.typ.callConv == ccClosure))
+
+  registerCallback c, "stdlib.formatfloat.addFloatRoundtrip", proc(a: VmArgs) =
+    let p = a.getVar(0)
+    let x = a.getFloat(1)
+    addFloatRoundtrip(p.strVal, x)
+
+  registerCallback c, "stdlib.formatfloat.addFloatSprintf", proc(a: VmArgs) =
+    let p = a.getVar(0)
+    let x = a.getFloat(1)
+    addFloatSprintf(p.strVal, x)